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39 >Privoxy 3.0.6 User Manual</TH
81 >14.1. Regular Expressions</H2
86 > uses Perl-style <SPAN
91 HREF="actions-file.html"
95 HREF="filter-file.html"
99 HREF="http://www.pcre.org/"
108 > If you are reading this, you probably don't understand what <SPAN
112 > are, or what they can do. So this will be a very brief
113 introduction only. A full explanation would require a <A
114 HREF="http://www.oreilly.com/catalog/regex/"
119 > Regular expressions provide a language to describe patterns that can be
120 run against strings of characters (letter, numbers, etc), to see if they
121 match the string or not. The patterns are themselves (sometimes complex)
122 strings of literal characters, combined with wild-cards, and other special
123 characters, called meta-characters. The <SPAN
125 >"meta-characters"</SPAN
127 special meanings and are used to build complex patterns to be matched against.
128 Perl Compatible Regular Expressions are an especially convenient
132 > of the regular expression language.</P
134 > To make a simple analogy, we do something similar when we use wild-card
135 characters when listing files with the <B
142 > matches all filenames. The <SPAN
146 character here is the asterisk which matches any and all characters. We can be
147 more specific and use <TT
150 > to match just individual
153 >"dir file?.text"</SPAN
161 >, etc. We are pattern
162 matching, using a similar technique to <SPAN
164 >"regular expressions"</SPAN
167 > Regular expressions do essentially the same thing, but are much, much more
168 powerful. There are many more <SPAN
170 >"special characters"</SPAN
172 building complex patterns however. Let's look at a few of the common ones,
173 and then some examples:</P
188 > - Matches any single character, e.g. <SPAN
226 > - The preceding character or expression is matched ZERO or ONE
249 > - The preceding character or expression is matched ONE or MORE
272 > - The preceding character or expression is matched ZERO or MORE
298 > character denotes that
299 the following character should be taken literally. This is used where one of the
300 special characters (e.g. <SPAN
303 >) needs to be taken literally and
304 not as a special meta-character. Example: <SPAN
306 >"example\.com"</SPAN
308 sure the period is recognized only as a period (and not expanded to its
309 meta-character meaning of any single character).
331 > - Characters enclosed in brackets will be matched if
332 any of the enclosed characters are encountered. For instance, <SPAN
336 matches any numeric digit (zero through nine). As an example, we can combine
340 > to match any digit one of more times: <SPAN
365 > - parentheses are used to group a sub-expression,
366 or multiple sub-expressions.
391 > character works like an
395 > conditional statement. A match is successful if the
396 sub-expression on either side of <SPAN
399 > matches. As an example:
402 >"/(this|that) example/"</SPAN
403 > uses grouping and the bar character
404 and would match either <SPAN
406 >"this example"</SPAN
420 > These are just some of the ones you are likely to use when matching URLs with
424 >, and is a long way from a definitive
425 list. This is enough to get us started with a few simple examples which may
426 be more illuminating:</P
438 that uses the common combination of <SPAN
445 denote any character, zero or more times. In other words, any string at all.
446 So we start with a literal forward slash, then our regular expression pattern
450 >) another literal forward slash, the string
454 >, another forward slash, and lastly another
459 a directory path here. This will match any file with the path that has a
460 directory named <SPAN
467 any characters, and this could conceivably be more forward slashes, so it
468 might expand into a much longer looking path. For example, this could match:
471 >"/eye/hate/spammers/banners/annoy_me_please.gif"</SPAN
475 >"/banners/annoying.html"</SPAN
476 >, or almost an infinite number of other
477 possible combinations, just so it has <SPAN
483 > And now something a little more complex:</P
491 >/.*/adv((er)?ts?|ertis(ing|ements?))?/</TT
495 We have several literal forward slashes again (<SPAN
499 building another expression that is a file path statement. We have another
503 >, so we are matching against any conceivable sub-path, just so
504 it matches our expression. The only true literal that <SPAN
511 > our pattern is <SPAN
515 the forward slashes. What comes after the <SPAN
519 interesting part. </P
524 > means the preceding expression (either a
525 literal character or anything grouped with <SPAN
529 can exist or not, since this means either zero or one match. So
532 >"((er)?ts?|ertis(ing|ements?))"</SPAN
533 > is optional, as are the
534 individual sub-expressions: <SPAN
540 >"(ing|ements?)"</SPAN
551 >. We have two of those. For instance,
554 >"(ing|ements?)"</SPAN
555 >, can expand to match either <SPAN
568 >. What is being done here, is an
569 attempt at matching as many variations of <SPAN
571 >"advertisement"</SPAN
573 similar, as possible. So this would expand to match just <SPAN
589 >"advertisement"</SPAN
593 >"advertisements"</SPAN
594 >. You get the idea. But it would not match
597 >"advertizements"</SPAN
601 >). We could fix that by
602 changing our regular expression to:
605 >"/.*/adv((er)?ts?|erti(s|z)(ing|ements?))?/"</SPAN
606 >, which would then match
615 >/.*/advert[0-9]+\.(gif|jpe?g)</TT
619 another path statement with forward slashes. Anything in the square brackets
623 > can be matched. This is using <SPAN
627 shorthand expression to mean any digit one through nine. It is the same as
631 >. So any digit matches. The <SPAN
635 means one or more of the preceding expression must be included. The preceding
636 expression here is what is in the square brackets -- in this case, any digit
637 one through nine. Then, at the end, we have a grouping: <SPAN
641 This includes a <SPAN
644 >, so this needs to match the expression on
645 either side of that bar character also. A simple <SPAN
648 > on one side, and the other
649 side will in turn match either <SPAN
659 > means the letter <SPAN
663 can be matched once or not at all. So we are building an expression here to
664 match image GIF or JPEG type image file. It must include the literal
668 >, then one or more digits, and a <SPAN
672 (which is now a literal, and not a special character, since it is escaped
676 >), and lastly either <SPAN
686 >. Some possible matches would
689 >"//advert1.jpg"</SPAN
693 >"/nasty/ads/advert1234.gif"</SPAN
697 >"/banners/from/hell/advert99.jpg"</SPAN
698 >. It would not match
702 > (no leading slash), or
705 >"/adverts232.jpg"</SPAN
706 > (the expression does not include an
712 >"/advert1.jsp"</SPAN
717 in the expression anywhere).</P
719 > We are barely scratching the surface of regular expressions here so that you
720 can understand the default <SPAN
724 configuration files, and maybe use this knowledge to customize your own
725 installation. There is much, much more that can be done with regular
726 expressions. Now that you know enough to get started, you can learn more on
729 > More reading on Perl Compatible Regular expressions:
731 HREF="http://perldoc.perl.org/perlre.html"
733 >http://perldoc.perl.org/perlre.html</A
736 > For information on regular expression based substitutions and their applications
737 in filters, please see the <A
738 HREF="filter-file.html"
739 >filter file tutorial</A
750 >14.2. Privoxy's Internal Pages</H2
755 > proxies each requested
756 web page, it is easy for <SPAN
760 trap certain special URLs. In this way, we can talk directly to
765 configured, see how our rules are being applied, change these
766 rules and other configuration options, and even turn
770 > filtering off, all with
771 a web browser. </P
773 > The URLs listed below are the special ones that allow direct access
781 > must be running to access these. If
782 not, you will get a friendly error message. Internet access is not
801 HREF="http://config.privoxy.org/"
803 >http://config.privoxy.org/</A
808 > There is a shortcut: <A
813 doesn't provide a fall-back to a real page, in case the request is not
823 Show information about the current configuration, including viewing and
824 editing of actions files:
834 HREF="http://config.privoxy.org/show-status"
836 >http://config.privoxy.org/show-status</A
844 Show the source code version numbers:
854 HREF="http://config.privoxy.org/show-version"
856 >http://config.privoxy.org/show-version</A
864 Show the browser's request headers:
874 HREF="http://config.privoxy.org/show-request"
876 >http://config.privoxy.org/show-request</A
884 Show which actions apply to a URL and why:
894 HREF="http://config.privoxy.org/show-url-info"
896 >http://config.privoxy.org/show-url-info</A
904 Toggle Privoxy on or off. In this case, <SPAN
908 to run, but only as a pass-through proxy, with no actions taking place:
918 HREF="http://config.privoxy.org/toggle"
920 >http://config.privoxy.org/toggle</A
925 > Short cuts. Turn off, then on:
935 HREF="http://config.privoxy.org/toggle?set=disable"
937 >http://config.privoxy.org/toggle?set=disable</A
949 HREF="http://config.privoxy.org/toggle?set=enable"
951 >http://config.privoxy.org/toggle?set=enable</A
959 > These may be bookmarked for quick reference. See next. </P
967 >14.2.1. Bookmarklets</H3
969 > Below are some <SPAN
971 >"bookmarklets"</SPAN
972 > to allow you to easily access a
976 > version of some of <SPAN
980 special pages. They are designed for MS Internet Explorer, but should work
981 equally well in Netscape, Mozilla, and other browsers which support
982 JavaScript. They are designed to run directly from your bookmarks - not by
983 clicking the links below (although that should work for testing).</P
985 > To save them, right-click the link and choose <SPAN
987 >"Add to Favorites"</SPAN
991 >"Add Bookmark"</SPAN
992 > (Netscape). You will get a warning that
995 >"may not be safe"</SPAN
996 > - just click OK. Then you can run the
997 Bookmarklet directly from your favorites/bookmarks. For even faster access,
998 you can put them on the <SPAN
1001 > bar (IE) or the <SPAN
1005 > (Netscape), and run them with a single click. </P
1013 HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y&set=enabled','ijbstatus','width=250,height=100,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
1015 >Privoxy - Enable</A
1022 HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y&set=disabled','ijbstatus','width=250,height=100,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
1024 >Privoxy - Disable</A
1031 HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y&set=toggle','ijbstatus','width=250,height=100,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
1033 >Privoxy - Toggle Privoxy</A
1034 > (Toggles between enabled and disabled)
1040 HREF="javascript:void(window.open('http://config.privoxy.org/toggle?mini=y','ijbstatus','width=250,height=2,resizable=yes,scrollbars=no,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
1042 >Privoxy- View Status</A
1049 HREF="javascript:void(window.open('http://config.privoxy.org/show-url-info?url='+escape(location.href),'Why').focus());"
1058 > Credit: The site which gave us the general idea for these bookmarklets is
1060 HREF="http://www.bookmarklets.com/"
1062 >www.bookmarklets.com</A
1064 have more information about bookmarklets. </P
1074 >14.3. Chain of Events</H2
1076 > Let's take a quick look at the basic sequence of events when a web page is
1077 requested by your browser and <SPAN
1087 > First, your web browser requests a web page. The browser knows to send
1088 the request to <SPAN
1091 >, which will in turn,
1092 relay the request to the remote web server after passing the following
1101 > traps any request for its own internal CGI
1106 >) and sends the CGI page back to the browser.
1114 > checks to see if the URL
1116 HREF="actions-file.html#BLOCK"
1122 so, the URL is then blocked, and the remote web server will not be contacted.
1124 HREF="actions-file.html#HANDLE-AS-IMAGE"
1127 >"+handle-as-image"</SPAN
1130 is then checked and if it does not match, an
1134 > page is sent back. Otherwise, if it does match,
1135 an image is returned. The type of image depends on the setting of <A
1136 HREF="actions-file.html#SET-IMAGE-BLOCKER"
1139 >"+set-image-blocker"</SPAN
1142 (blank, checkerboard pattern, or an HTTP redirect to an image elsewhere).
1147 > Untrusted URLs are blocked. If URLs are being added to the
1151 > file, then that is done.
1156 > If the URL pattern matches the <A
1157 HREF="actions-file.html#FAST-REDIRECTS"
1160 >"+fast-redirects"</SPAN
1163 it is then processed. Unwanted parts of the requested URL are stripped.
1168 > Now the rest of the client browser's request headers are processed. If any
1169 of these match any of the relevant actions (e.g. <A
1170 HREF="actions-file.html#HIDE-USER-AGENT"
1173 >"+hide-user-agent"</SPAN
1176 etc.), headers are suppressed or forged as determined by these actions and
1182 > Now the web server starts sending its response back (i.e. typically a web page and related
1188 > First, the server headers are read and processed to determine, among other
1189 things, the MIME type (document type) and encoding. The headers are then
1190 filtered as determined by the
1192 HREF="actions-file.html#CRUNCH-INCOMING-COOKIES"
1195 >"+crunch-incoming-cookies"</SPAN
1199 HREF="actions-file.html#SESSION-COOKIES-ONLY"
1202 >"+session-cookies-only"</SPAN
1206 HREF="actions-file.html#DOWNGRADE-HTTP-VERSION"
1209 >"+downgrade-http-version"</SPAN
1218 HREF="actions-file.html#KILL-POPUPS"
1221 >"+kill-popups"</SPAN
1224 action applies, and it is an HTML or JavaScript document, the popup-code in the
1225 response is filtered on-the-fly as it is received.
1231 HREF="actions-file.html#FILTER"
1238 HREF="actions-file.html#DEANIMATE-GIFS"
1241 >"+deanimate-gifs"</SPAN
1244 action applies (and the document type fits the action), the rest of the page is
1245 read into memory (up to a configurable limit). Then the filter rules (from
1249 > and any other filter files) are
1250 processed against the buffered content. Filters are applied in the order
1251 they are specified in one of the filter files. Animated GIFs, if present,
1252 are reduced to either the first or last frame, depending on the action
1253 setting.The entire page, which is now filtered, is then sent by
1257 > back to your browser.
1261 HREF="actions-file.html#FILTER"
1268 HREF="actions-file.html#DEANIMATE-GIFS"
1271 >"+deanimate-gifs"</SPAN
1277 > passes the raw data through
1278 to the client browser as it becomes available.
1283 > As the browser receives the now (possibly filtered) page content, it
1284 reads and then requests any URLs that may be embedded within the page
1285 source, e.g. ad images, stylesheets, JavaScript, other HTML documents (e.g.
1286 frames), sounds, etc. For each of these objects, the browser issues a new
1287 request. And each such request is in turn processed as above. Note that a
1288 complex web page may have many such embedded URLs.
1301 >14.4. Troubleshooting: Anatomy of an Action</H2
1308 HREF="actions-file.html#ACTIONS"
1311 HREF="actions-file.html#FILTER"
1314 to any given URL can be complex, and not always so
1315 easy to understand what is happening. And sometimes we need to be able to
1326 doing. Especially, if something <SPAN
1330 is causing us a problem inadvertently. It can be a little daunting to look at
1331 the actions and filters files themselves, since they tend to be filled with
1333 HREF="appendix.html#REGEX"
1334 >regular expressions</A
1335 > whose consequences are not
1336 always so obvious. </P
1338 > One quick test to see if <SPAN
1341 > is causing a problem
1342 or not, is to disable it temporarily. This should be the first troubleshooting
1344 HREF="appendix.html#BOOKMARKLETS"
1345 >the Bookmarklets</A
1346 > section on a quick
1347 and easy way to do this (be sure to flush caches afterward!). Looking at the
1348 logs is a good idea too.</P
1350 > Another easy troubleshooting step to try is if you have done any
1351 customization of your installation, revert back to the installed
1352 defaults and see if that helps. There are times the developers get complaints
1353 about one thing or another, and the problem is more related to a customized
1354 configuration issue.</P
1361 HREF="http://config.privoxy.org/show-url-info"
1363 >http://config.privoxy.org/show-url-info</A
1365 page that can show us very specifically how <SPAN
1369 are being applied to any given URL. This is a big help for troubleshooting.</P
1371 > First, enter one URL (or partial URL) at the prompt, and then
1376 how the current configuration will handle it. This will not
1377 help with filtering effects (i.e. the <A
1378 HREF="actions-file.html#FILTER"
1384 one of the filter files since this is handled very
1385 differently and not so easy to trap! It also will not tell you about any other
1386 URLs that may be embedded within the URL you are testing. For instance, images
1387 such as ads are expressed as URLs within the raw page source of HTML pages. So
1388 you will only get info for the actual URL that is pasted into the prompt area
1389 -- not any sub-URLs. If you want to know about embedded URLs like ads, you
1390 will have to dig those out of the HTML source. Use your browser's <SPAN
1394 > option for this. Or right click on the ad, and grab the
1397 > Let's try an example, <A
1398 HREF="http://google.com"
1402 and look at it one section at a time in a sample configuration (your real
1403 configuration may vary):</P
1413 > Matches for http://google.com:
1415 In file: default.action <SPAN
1425 -content-type-overwrite
1426 -crunch-client-header
1427 -crunch-if-none-match
1428 -crunch-incoming-cookies
1429 -crunch-outgoing-cookies
1430 -crunch-server-header
1431 +deanimate-gifs {last}
1432 -downgrade-http-version
1433 +fast-redirects {check-decoded-url}
1435 -filter {content-cookies}
1436 -filter {all-popups}
1437 -filter {banners-by-link}
1438 -filter {tiny-textforms}
1439 -filter {frameset-borders}
1440 -filter {demoronizer}
1441 -filter {shockwave-flash}
1442 -filter {quicktime-kioskmode}
1444 -filter {crude-parental}
1445 -filter {site-specifics}
1446 -filter {js-annoyances}
1447 -filter {html-annoyances}
1448 +filter {refresh-tags}
1449 -filter {unsolicited-popups}
1450 +filter {img-reorder}
1451 +filter {banners-by-size}
1453 +filter {jumping-windows}
1454 +filter {ie-exploits}
1459 -filter {xml-to-html}
1460 -filter {html-to-xml}
1461 -filter-client-headers
1462 -filter-server-headers
1464 -handle-as-empty-document
1466 -hide-accept-language
1467 -hide-content-disposition
1468 +hide-forwarded-for-headers
1469 +hide-from-header {block}
1470 -hide-if-modified-since
1471 +hide-referrer {forge}
1476 -overwrite-last-modified
1477 +prevent-compression
1481 +session-cookies-only
1482 +set-image-blocker {pattern}
1483 -treat-forbidden-connects-like-blocks }
1486 { -session-cookies-only }
1492 In file: user.action <SPAN
1499 (no matches in this file) </PRE
1505 > This is telling us how we have defined our
1507 HREF="actions-file.html#ACTIONS"
1513 which ones match for our test case, <SPAN
1517 Displayed is all the actions that are available to us. Remember,
1521 > sign denotes <SPAN
1531 >. So some are <SPAN
1538 >. Each example we try may provide a slightly different
1539 end result, depending on our configuration directives.</P
1545 > file. The large, multi-line
1546 listing, is how the actions are set to match for all URLs, i.e. our default
1547 settings. If you look at your <SPAN
1550 > file, this would be the
1551 section just below the <SPAN
1554 > section near the top. This
1555 will apply to all URLs as signified by the single forward slash at the end
1556 of the listing -- <SPAN
1561 > But we have defined additional actions that would be exceptions to these general
1562 rules, and then we list specific URLs (or patterns) that these exceptions
1563 would apply to. Last match wins. Just below this then are two explicit
1566 >".google.com"</SPAN
1567 >. The first is negating our previous
1568 cookie setting, which was for <A
1569 HREF="actions-file.html#SESSION-COOKIES-ONLY"
1572 >"+session-cookies-only"</SPAN
1575 (i.e. not persistent). So we will allow persistent cookies for google, at
1576 least that is how it is in this example. The second turns
1584 HREF="actions-file.html#FAST-REDIRECTS"
1587 >"+fast-redirects"</SPAN
1590 action, allowing this to take place unmolested. Note that there is a leading
1593 >".google.com"</SPAN
1594 >. This will match any hosts and
1595 sub-domains, in the google.com domain also, such as
1598 >"www.google.com"</SPAN
1601 >"mail.google.com"</SPAN
1605 >"www.google.de"</SPAN
1606 >! So, apparently, we have these two actions
1607 defined as exceptions to the general rules at the top somewhere in the lower
1615 > is referenced somewhere in these latter sections.</P
1620 > file, we again have no hits.
1621 So there is nothing google-specific that we might have added to our own, local
1622 configuration. If there was, those actions would over-rule any actions from
1623 previously processed files, such as <TT
1630 > typically has the last word. This is the
1631 best place to put hard and fast exceptions,</P
1633 > And finally we pull it all together in the bottom section and summarize how
1637 > is applying all its <SPAN
1654 > Final results:
1658 -content-type-overwrite
1659 -crunch-client-header
1660 -crunch-if-none-match
1661 -crunch-incoming-cookies
1662 -crunch-outgoing-cookies
1663 -crunch-server-header
1664 +deanimate-gifs {last}
1665 -downgrade-http-version
1666 +fast-redirects {check-decoded-url}
1668 -filter {content-cookies}
1669 -filter {all-popups}
1670 -filter {banners-by-link}
1671 -filter {tiny-textforms}
1672 -filter {frameset-borders}
1673 -filter {demoronizer}
1674 -filter {shockwave-flash}
1675 -filter {quicktime-kioskmode}
1677 -filter {crude-parental}
1678 -filter {site-specifics}
1679 -filter {js-annoyances}
1680 -filter {html-annoyances}
1681 +filter {refresh-tags}
1682 -filter {unsolicited-popups}
1683 +filter {img-reorder}
1684 +filter {banners-by-size}
1686 +filter {jumping-windows}
1687 +filter {ie-exploits}
1692 -filter {xml-to-html}
1693 -filter {html-to-xml}
1694 -filter-client-headers
1695 -filter-server-headers
1697 -handle-as-empty-document
1699 -hide-accept-language
1700 -hide-content-disposition
1701 +hide-forwarded-for-headers
1702 +hide-from-header {block}
1703 -hide-if-modified-since
1704 +hide-referrer {forge}
1709 -overwrite-last-modified
1710 +prevent-compression
1714 -session-cookies-only
1715 +set-image-blocker {pattern}
1716 -treat-forbidden-connects-like-blocks </PRE
1722 > Notice the only difference here to the previous listing, is to
1725 >"fast-redirects"</SPAN
1728 >"session-cookies-only"</SPAN
1730 which are activated specifically for this site in our configuration,
1731 and thus show in the <SPAN
1733 >"Final Results"</SPAN
1736 > Now another example, <SPAN
1738 >"ad.doubleclick.net"</SPAN
1755 { +block +handle-as-image }
1756 .[a-vx-z]*.doubleclick.net</PRE
1762 > We'll just show the interesting part here - the explicit matches. It is
1763 matched three different times. Two <SPAN
1769 >"+block +handle-as-image"</SPAN
1771 which is the expanded form of one of our aliases that had been defined as:
1774 >"+block-as-image"</SPAN
1776 HREF="actions-file.html#ALIASES"
1782 the first section of the actions file and typically used to combine more
1783 than one action.)</P
1785 > Any one of these would have done the trick and blocked this as an unwanted
1786 image. This is unnecessarily redundant since the last case effectively
1787 would also cover the first. No point in taking chances with these guys
1788 though ;-) Note that if you want an ad or obnoxious
1789 URL to be invisible, it should be defined as <SPAN
1791 >"ad.doubleclick.net"</SPAN
1793 is done here -- as both a <A
1794 HREF="actions-file.html#BLOCK"
1808 HREF="actions-file.html#HANDLE-AS-IMAGE"
1811 >"+handle-as-image"</SPAN
1814 The custom alias <SPAN
1818 >+block-as-image</TT
1821 simplifies the process and make it more readable.</P
1823 > One last example. Let's try <SPAN
1825 >"http://www.example.net/adsl/HOWTO/"</SPAN
1827 This one is giving us problems. We are getting a blank page. Hmmm ...</P
1837 > Matches for http://www.example.net/adsl/HOWTO/:
1839 In file: default.action <SPAN
1849 -content-type-overwrite
1850 -crunch-client-header
1851 -crunch-if-none-match
1852 -crunch-incoming-cookies
1853 -crunch-outgoing-cookies
1854 -crunch-server-header
1856 -downgrade-http-version
1857 +fast-redirects {check-decoded-url}
1859 -filter {content-cookies}
1860 -filter {all-popups}
1861 -filter {banners-by-link}
1862 -filter {tiny-textforms}
1863 -filter {frameset-borders}
1864 -filter {demoronizer}
1865 -filter {shockwave-flash}
1866 -filter {quicktime-kioskmode}
1868 -filter {crude-parental}
1869 -filter {site-specifics}
1870 -filter {js-annoyances}
1871 -filter {html-annoyances}
1872 +filter {refresh-tags}
1873 -filter {unsolicited-popups}
1874 +filter {img-reorder}
1875 +filter {banners-by-size}
1877 +filter {jumping-windows}
1878 +filter {ie-exploits}
1883 -filter {xml-to-html}
1884 -filter {html-to-xml}
1885 -filter-client-headers
1886 -filter-server-headers
1888 -handle-as-empty-document
1890 -hide-accept-language
1891 -hide-content-disposition
1892 +hide-forwarded-for-headers
1893 +hide-from-header{block}
1894 +hide-referer{forge}
1898 -overwrite-last-modified
1899 +prevent-compression
1903 +session-cookies-only
1904 +set-image-blocker{blank}
1905 -treat-forbidden-connects-like-blocks }
1908 { +block +handle-as-image }
1922 configuration! But we did not want this at all! Now we see why we get the
1923 blank page. It is actually triggering two different actions here, and
1924 the effects are aggregated so that the URL is blocked, and <SPAN
1928 to treat the block as if it were an image. But this is, of course, all wrong.
1929 We could now add a new action below this (or better in our own
1933 > file) that explicitly
1942 HREF="actions-file.html#BLOCK"
1951 > in them (remember, last match in the configuration
1952 wins). There are various ways to handle such exceptions. Example:</P
1969 > Now the page displays ;-)
1970 Remember to flush your browser's caches when making these kinds of changes to
1971 your configuration to insure that you get a freshly delivered page! Or, try
1977 > But now what about a situation where we get no explicit matches like
1988 > { +block +handle-as-image }
1995 > That actually was very helpful and pointed us quickly to where the problem
1996 was. If you don't get this kind of match, then it means one of the default
1997 rules in the first section of <TT
2001 the problem. This would require some guesswork, and maybe a little trial and
2002 error to isolate the offending rule. One likely cause would be one of the
2004 HREF="actions-file.html#FILTER"
2010 These tend to be harder to troubleshoot.
2011 Try adding the URL for the site to one of aliases that turn off
2013 HREF="actions-file.html#FILTER"
2030 .worldpay.com # for quietpc.com
2053 >{ -filter -session-cookies-only }</TT
2056 Or you could do your own exception to negate filtering: </P
2067 # Disable ALL filter actions for sites in this section
2076 > This would turn off all filtering for these sites. This is best
2081 exceptions. Note that when a simple domain pattern is used by itself (without
2082 the subsequent path portion), all sub-pages within that domain are included
2083 automatcially in the scope of the action.</P
2085 > Images that are inexplicably being blocked, may well be hitting the
2087 HREF="actions-file.html#FILTER-BANNERS-BY-SIZE"
2090 >"+filter{banners-by-size}"</SPAN
2094 that images of certain sizes are ad banners (works well
2099 >most of the time</I
2101 > since these tend to be standardized).</P
2109 > is an alias that disables most
2110 actions that are the most likely to cause trouble. This can be used as a
2111 last resort for problem sites. </P
2122 # Handle with care: easy to break
2124 mybank.example.com</PRE
2134 >Remember to flush caches!</I
2140 > reference lacks the TLD portion (e.g.
2144 >. This will effectively match any TLD with
2148 > in it, such as <TT
2152 just as an example.</P
2155 If this still does not work, you will have to go through the remaining
2156 actions one by one to find which one(s) is causing the problem.</P
2164 SUMMARY="Footer navigation table"