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39 >Privoxy 3.0.7 User Manual</TH
80 >14.1. Regular Expressions</A
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
749 >14.2. Privoxy's Internal Pages</A
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. This feature can be turned off/on in the main
908 > file. When toggled <SPAN
915 continues to run, but only as a pass-through proxy, with no actions taking
926 HREF="http://config.privoxy.org/toggle"
928 >http://config.privoxy.org/toggle</A
933 > Short cuts. Turn off, then on:
943 HREF="http://config.privoxy.org/toggle?set=disable"
945 >http://config.privoxy.org/toggle?set=disable</A
957 HREF="http://config.privoxy.org/toggle?set=enable"
959 >http://config.privoxy.org/toggle?set=enable</A
967 > These may be bookmarked for quick reference. See next. </P
974 >14.2.1. Bookmarklets</A
977 > Below are some <SPAN
979 >"bookmarklets"</SPAN
980 > to allow you to easily access a
984 > version of some of <SPAN
988 special pages. They are designed for MS Internet Explorer, but should work
989 equally well in Netscape, Mozilla, and other browsers which support
990 JavaScript. They are designed to run directly from your bookmarks - not by
991 clicking the links below (although that should work for testing).</P
993 > To save them, right-click the link and choose <SPAN
995 >"Add to Favorites"</SPAN
999 >"Add Bookmark"</SPAN
1000 > (Netscape). You will get a warning that
1003 >"may not be safe"</SPAN
1004 > - just click OK. Then you can run the
1005 Bookmarklet directly from your favorites/bookmarks. For even faster access,
1006 you can put them on the <SPAN
1009 > bar (IE) or the <SPAN
1013 > (Netscape), and run them with a single click. </P
1021 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());"
1023 >Privoxy - Enable</A
1030 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());"
1032 >Privoxy - Disable</A
1039 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());"
1041 >Privoxy - Toggle Privoxy</A
1042 > (Toggles between enabled and disabled)
1048 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());"
1050 >Privoxy- View Status</A
1057 HREF="javascript:void(window.open('http://config.privoxy.org/show-url-info?url='+escape(location.href),'Why').focus());"
1066 > Credit: The site which gave us the general idea for these bookmarklets is
1068 HREF="http://www.bookmarklets.com/"
1070 >www.bookmarklets.com</A
1072 have more information about bookmarklets. </P
1081 >14.3. Chain of Events</A
1084 > Let's take a quick look at how some of <SPAN
1088 core features are triggered, and the ensuing sequence of events when a web
1089 page is requested by your browser:</P
1096 > First, your web browser requests a web page. The browser knows to send
1097 the request to <SPAN
1100 >, which will in turn,
1101 relay the request to the remote web server after passing the following
1110 > traps any request for its own internal CGI
1115 >) and sends the CGI page back to the browser.
1123 > checks to see if the URL
1125 HREF="actions-file.html#BLOCK"
1131 so, the URL is then blocked, and the remote web server will not be contacted.
1133 HREF="actions-file.html#HANDLE-AS-IMAGE"
1136 >"+handle-as-image"</SPAN
1141 HREF="actions-file.html#HANDLE-AS-EMPTY-DOCUMENT"
1144 >"+handle-as-empty-document"</SPAN
1147 are then checked, and if there is no match, an
1151 > page is sent back to the browser. Otherwise, if
1152 it does match, an image is returned for the former, and an empty text
1153 document for the latter. The type of image would depend on the setting of
1155 HREF="actions-file.html#SET-IMAGE-BLOCKER"
1158 >"+set-image-blocker"</SPAN
1161 (blank, checkerboard pattern, or an HTTP redirect to an image elsewhere).
1166 > Untrusted URLs are blocked. If URLs are being added to the
1170 > file, then that is done.
1175 > If the URL pattern matches the <A
1176 HREF="actions-file.html#FAST-REDIRECTS"
1179 >"+fast-redirects"</SPAN
1182 it is then processed. Unwanted parts of the requested URL are stripped.
1187 > Now the rest of the client browser's request headers are processed. If any
1188 of these match any of the relevant actions (e.g. <A
1189 HREF="actions-file.html#HIDE-USER-AGENT"
1192 >"+hide-user-agent"</SPAN
1195 etc.), headers are suppressed or forged as determined by these actions and
1201 > Now the web server starts sending its response back (i.e. typically a web
1207 > First, the server headers are read and processed to determine, among other
1208 things, the MIME type (document type) and encoding. The headers are then
1209 filtered as determined by the
1211 HREF="actions-file.html#CRUNCH-INCOMING-COOKIES"
1214 >"+crunch-incoming-cookies"</SPAN
1218 HREF="actions-file.html#SESSION-COOKIES-ONLY"
1221 >"+session-cookies-only"</SPAN
1225 HREF="actions-file.html#DOWNGRADE-HTTP-VERSION"
1228 >"+downgrade-http-version"</SPAN
1237 HREF="actions-file.html#KILL-POPUPS"
1240 >"+kill-popups"</SPAN
1243 action applies, and it is an HTML or JavaScript document, the popup-code in the
1244 response is filtered on-the-fly as it is received.
1250 HREF="actions-file.html#FILTER"
1257 HREF="actions-file.html#DEANIMATE-GIFS"
1260 >"+deanimate-gifs"</SPAN
1263 action applies (and the document type fits the action), the rest of the page is
1264 read into memory (up to a configurable limit). Then the filter rules (from
1268 > and any other filter files) are
1269 processed against the buffered content. Filters are applied in the order
1270 they are specified in one of the filter files. Animated GIFs, if present,
1271 are reduced to either the first or last frame, depending on the action
1272 setting.The entire page, which is now filtered, is then sent by
1276 > back to your browser.
1280 HREF="actions-file.html#FILTER"
1287 HREF="actions-file.html#DEANIMATE-GIFS"
1290 >"+deanimate-gifs"</SPAN
1296 > passes the raw data through
1297 to the client browser as it becomes available.
1302 > As the browser receives the now (possibly filtered) page content, it
1303 reads and then requests any URLs that may be embedded within the page
1304 source, e.g. ad images, stylesheets, JavaScript, other HTML documents (e.g.
1305 frames), sounds, etc. For each of these objects, the browser issues a
1306 separate request (this is easily viewable in <SPAN
1310 logs). And each such request is in turn processed just as above. Note that a
1311 complex web page will have many, many such embedded URLs. If these
1312 secondary requests are to a different server, then quite possibly a very
1313 differing set of actions is triggered.
1319 > NOTE: This is somewhat of a simplistic overview of what happens with each URL
1320 request. For the sake of brevity and simplicity, we have focused on
1324 > core features only.</P
1332 >14.4. Troubleshooting: Anatomy of an Action</A
1340 HREF="actions-file.html#ACTIONS"
1343 HREF="actions-file.html#FILTER"
1346 to any given URL can be complex, and not always so
1347 easy to understand what is happening. And sometimes we need to be able to
1358 doing. Especially, if something <SPAN
1362 is causing us a problem inadvertently. It can be a little daunting to look at
1363 the actions and filters files themselves, since they tend to be filled with
1365 HREF="appendix.html#REGEX"
1366 >regular expressions</A
1367 > whose consequences are not
1368 always so obvious. </P
1370 > One quick test to see if <SPAN
1373 > is causing a problem
1374 or not, is to disable it temporarily. This should be the first troubleshooting
1376 HREF="appendix.html#BOOKMARKLETS"
1377 >the Bookmarklets</A
1378 > section on a quick
1379 and easy way to do this (be sure to flush caches afterward!). Looking at the
1380 logs is a good idea too. (Note that both the toggle feature and logging are
1384 > file settings, and may need to be
1390 > Another easy troubleshooting step to try is if you have done any
1391 customization of your installation, revert back to the installed
1392 defaults and see if that helps. There are times the developers get complaints
1393 about one thing or another, and the problem is more related to a customized
1394 configuration issue.</P
1401 HREF="http://config.privoxy.org/show-url-info"
1403 >http://config.privoxy.org/show-url-info</A
1405 page that can show us very specifically how <SPAN
1409 are being applied to any given URL. This is a big help for troubleshooting.</P
1411 > First, enter one URL (or partial URL) at the prompt, and then
1416 how the current configuration will handle it. This will not
1417 help with filtering effects (i.e. the <A
1418 HREF="actions-file.html#FILTER"
1424 one of the filter files since this is handled very
1425 differently and not so easy to trap! It also will not tell you about any other
1426 URLs that may be embedded within the URL you are testing. For instance, images
1427 such as ads are expressed as URLs within the raw page source of HTML pages. So
1428 you will only get info for the actual URL that is pasted into the prompt area
1429 -- not any sub-URLs. If you want to know about embedded URLs like ads, you
1430 will have to dig those out of the HTML source. Use your browser's <SPAN
1434 > option for this. Or right click on the ad, and grab the
1437 > Let's try an example, <A
1438 HREF="http://google.com"
1442 and look at it one section at a time in a sample configuration (your real
1443 configuration may vary):</P
1453 > Matches for http://www.google.com:
1455 In file: default.action <SPAN
1463 {+deanimate-gifs {last}
1464 +fast-redirects {check-decoded-url}
1465 +filter {refresh-tags}
1466 +filter {img-reorder}
1467 +filter {banners-by-size}
1469 +filter {jumping-windows}
1470 +filter {ie-exploits}
1471 +hide-forwarded-for-headers
1472 +hide-from-header {block}
1473 +hide-referrer {forge}
1474 +session-cookies-only
1475 +set-image-blocker {pattern}
1478 { -session-cookies-only }
1484 In file: user.action <SPAN
1491 (no matches in this file) </PRE
1497 > This is telling us how we have defined our
1499 HREF="actions-file.html#ACTIONS"
1505 which ones match for our test case, <SPAN
1509 Displayed is all the actions that are available to us. Remember,
1513 > sign denotes <SPAN
1523 >. So some are <SPAN
1530 >. Each example we try may provide a slightly different
1531 end result, depending on our configuration directives.</P
1537 > file. The large, multi-line
1538 listing, is how the actions are set to match for all URLs, i.e. our default
1539 settings. If you look at your <SPAN
1542 > file, this would be the
1543 section just below the <SPAN
1546 > section near the top. This
1547 will apply to all URLs as signified by the single forward slash at the end
1548 of the listing -- <SPAN
1553 > But we have defined additional actions that would be exceptions to these general
1554 rules, and then we list specific URLs (or patterns) that these exceptions
1555 would apply to. Last match wins. Just below this then are two explicit
1558 >".google.com"</SPAN
1559 >. The first is negating our previous
1560 cookie setting, which was for <A
1561 HREF="actions-file.html#SESSION-COOKIES-ONLY"
1564 >"+session-cookies-only"</SPAN
1567 (i.e. not persistent). So we will allow persistent cookies for google, at
1568 least that is how it is in this example. The second turns
1576 HREF="actions-file.html#FAST-REDIRECTS"
1579 >"+fast-redirects"</SPAN
1582 action, allowing this to take place unmolested. Note that there is a leading
1585 >".google.com"</SPAN
1586 >. This will match any hosts and
1587 sub-domains, in the google.com domain also, such as
1590 >"www.google.com"</SPAN
1593 >"mail.google.com"</SPAN
1597 >"www.google.de"</SPAN
1598 >! So, apparently, we have these two actions
1599 defined as exceptions to the general rules at the top somewhere in the lower
1607 > is referenced somewhere in these latter sections.</P
1612 > file, we again have no hits.
1613 So there is nothing google-specific that we might have added to our own, local
1614 configuration. If there was, those actions would over-rule any actions from
1615 previously processed files, such as <TT
1622 > typically has the last word. This is the
1623 best place to put hard and fast exceptions,</P
1625 > And finally we pull it all together in the bottom section and summarize how
1629 > is applying all its <SPAN
1646 > Final results:
1650 -client-header-filter{hide-tor-exit-notation}
1651 -content-type-overwrite
1652 -crunch-client-header
1653 -crunch-if-none-match
1654 -crunch-incoming-cookies
1655 -crunch-outgoing-cookies
1656 -crunch-server-header
1657 +deanimate-gifs {last}
1658 -downgrade-http-version
1661 -filter {content-cookies}
1662 -filter {all-popups}
1663 -filter {banners-by-link}
1664 -filter {tiny-textforms}
1665 -filter {frameset-borders}
1666 -filter {demoronizer}
1667 -filter {shockwave-flash}
1668 -filter {quicktime-kioskmode}
1670 -filter {crude-parental}
1671 -filter {site-specifics}
1672 -filter {js-annoyances}
1673 -filter {html-annoyances}
1674 +filter {refresh-tags}
1675 -filter {unsolicited-popups}
1676 +filter {img-reorder}
1677 +filter {banners-by-size}
1679 +filter {jumping-windows}
1680 +filter {ie-exploits}
1687 -handle-as-empty-document
1689 -hide-accept-language
1690 -hide-content-disposition
1691 +hide-forwarded-for-headers
1692 +hide-from-header {block}
1693 -hide-if-modified-since
1694 +hide-referrer {forge}
1699 -overwrite-last-modified
1700 -prevent-compression
1704 -server-header-filter{xml-to-html}
1705 -server-header-filter{html-to-xml}
1706 -session-cookies-only
1707 +set-image-blocker {pattern}
1708 -treat-forbidden-connects-like-blocks </PRE
1714 > Notice the only difference here to the previous listing, is to
1717 >"fast-redirects"</SPAN
1720 >"session-cookies-only"</SPAN
1722 which are activated specifically for this site in our configuration,
1723 and thus show in the <SPAN
1725 >"Final Results"</SPAN
1728 > Now another example, <SPAN
1730 >"ad.doubleclick.net"</SPAN
1747 { +block +handle-as-image }
1748 .[a-vx-z]*.doubleclick.net</PRE
1754 > We'll just show the interesting part here - the explicit matches. It is
1755 matched three different times. Two <SPAN
1761 >"+block +handle-as-image"</SPAN
1763 which is the expanded form of one of our aliases that had been defined as:
1766 >"+block-as-image"</SPAN
1768 HREF="actions-file.html#ALIASES"
1774 the first section of the actions file and typically used to combine more
1775 than one action.)</P
1777 > Any one of these would have done the trick and blocked this as an unwanted
1778 image. This is unnecessarily redundant since the last case effectively
1779 would also cover the first. No point in taking chances with these guys
1780 though ;-) Note that if you want an ad or obnoxious
1781 URL to be invisible, it should be defined as <SPAN
1783 >"ad.doubleclick.net"</SPAN
1785 is done here -- as both a <A
1786 HREF="actions-file.html#BLOCK"
1800 HREF="actions-file.html#HANDLE-AS-IMAGE"
1803 >"+handle-as-image"</SPAN
1806 The custom alias <SPAN
1810 >+block-as-image</TT
1813 simplifies the process and make it more readable.</P
1815 > One last example. Let's try <SPAN
1817 >"http://www.example.net/adsl/HOWTO/"</SPAN
1819 This one is giving us problems. We are getting a blank page. Hmmm ...</P
1829 > Matches for http://www.example.net/adsl/HOWTO/:
1831 In file: default.action <SPAN
1841 -client-header-filter{hide-tor-exit-notation}
1842 -content-type-overwrite
1843 -crunch-client-header
1844 -crunch-if-none-match
1845 -crunch-incoming-cookies
1846 -crunch-outgoing-cookies
1847 -crunch-server-header
1849 -downgrade-http-version
1850 +fast-redirects {check-decoded-url}
1852 -filter {content-cookies}
1853 -filter {all-popups}
1854 -filter {banners-by-link}
1855 -filter {tiny-textforms}
1856 -filter {frameset-borders}
1857 -filter {demoronizer}
1858 -filter {shockwave-flash}
1859 -filter {quicktime-kioskmode}
1861 -filter {crude-parental}
1862 -filter {site-specifics}
1863 -filter {js-annoyances}
1864 -filter {html-annoyances}
1865 +filter {refresh-tags}
1866 -filter {unsolicited-popups}
1867 +filter {img-reorder}
1868 +filter {banners-by-size}
1870 +filter {jumping-windows}
1871 +filter {ie-exploits}
1878 -handle-as-empty-document
1880 -hide-accept-language
1881 -hide-content-disposition
1882 +hide-forwarded-for-headers
1883 +hide-from-header{block}
1884 +hide-referer{forge}
1888 -overwrite-last-modified
1889 +prevent-compression
1893 -server-header-filter{xml-to-html}
1894 -server-header-filter{html-to-xml}
1895 +session-cookies-only
1896 +set-image-blocker{blank}
1897 -treat-forbidden-connects-like-blocks }
1900 { +block +handle-as-image }
1914 configuration! But we did not want this at all! Now we see why we get the
1915 blank page. It is actually triggering two different actions here, and
1916 the effects are aggregated so that the URL is blocked, and <SPAN
1920 to treat the block as if it were an image. But this is, of course, all wrong.
1921 We could now add a new action below this (or better in our own
1925 > file) that explicitly
1934 HREF="actions-file.html#BLOCK"
1943 > in them (remember, last match in the configuration
1944 wins). There are various ways to handle such exceptions. Example:</P
1961 > Now the page displays ;-)
1962 Remember to flush your browser's caches when making these kinds of changes to
1963 your configuration to insure that you get a freshly delivered page! Or, try
1969 > But now what about a situation where we get no explicit matches like
1980 > { +block +handle-as-image }
1987 > That actually was very helpful and pointed us quickly to where the problem
1988 was. If you don't get this kind of match, then it means one of the default
1989 rules in the first section of <TT
1993 the problem. This would require some guesswork, and maybe a little trial and
1994 error to isolate the offending rule. One likely cause would be one of the
1996 HREF="actions-file.html#FILTER"
2002 These tend to be harder to troubleshoot.
2003 Try adding the URL for the site to one of aliases that turn off
2005 HREF="actions-file.html#FILTER"
2022 .worldpay.com # for quietpc.com
2045 >{ -filter -session-cookies-only }</TT
2048 Or you could do your own exception to negate filtering: </P
2059 # Disable ALL filter actions for sites in this section
2068 > This would turn off all filtering for these sites. This is best
2073 exceptions. Note that when a simple domain pattern is used by itself (without
2074 the subsequent path portion), all sub-pages within that domain are included
2075 automatically in the scope of the action.</P
2077 > Images that are inexplicably being blocked, may well be hitting the
2079 HREF="actions-file.html#FILTER-BANNERS-BY-SIZE"
2082 >"+filter{banners-by-size}"</SPAN
2086 that images of certain sizes are ad banners (works well
2091 >most of the time</I
2093 > since these tend to be standardized).</P
2101 > is an alias that disables most
2102 actions that are the most likely to cause trouble. This can be used as a
2103 last resort for problem sites. </P
2114 # Handle with care: easy to break
2116 mybank.example.com</PRE
2126 >Remember to flush caches!</I
2132 > reference lacks the TLD portion (e.g.
2136 >). This will effectively match any TLD with
2140 > in it, such as <TT
2142 >mail.google.de.</TT
2144 just as an example.</P
2147 If this still does not work, you will have to go through the remaining
2148 actions one by one to find which one(s) is causing the problem.</P
2156 SUMMARY="Footer navigation table"