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42 >Privoxy 3.0.11 User Manual</TH
83 >14.1. Regular Expressions</A
89 > uses Perl-style <SPAN
94 HREF="actions-file.html"
98 HREF="filter-file.html"
102 HREF="http://www.pcre.org/"
111 > If you are reading this, you probably don't understand what <SPAN
115 > are, or what they can do. So this will be a very brief
116 introduction only. A full explanation would require a <A
117 HREF="http://www.oreilly.com/catalog/regex/"
122 > Regular expressions provide a language to describe patterns that can be
123 run against strings of characters (letter, numbers, etc), to see if they
124 match the string or not. The patterns are themselves (sometimes complex)
125 strings of literal characters, combined with wild-cards, and other special
126 characters, called meta-characters. The <SPAN
128 >"meta-characters"</SPAN
130 special meanings and are used to build complex patterns to be matched against.
131 Perl Compatible Regular Expressions are an especially convenient
135 > of the regular expression language.</P
137 > To make a simple analogy, we do something similar when we use wild-card
138 characters when listing files with the <B
145 > matches all filenames. The <SPAN
149 character here is the asterisk which matches any and all characters. We can be
150 more specific and use <TT
153 > to match just individual
156 >"dir file?.text"</SPAN
164 >, etc. We are pattern
165 matching, using a similar technique to <SPAN
167 >"regular expressions"</SPAN
170 > Regular expressions do essentially the same thing, but are much, much more
171 powerful. There are many more <SPAN
173 >"special characters"</SPAN
175 building complex patterns however. Let's look at a few of the common ones,
176 and then some examples:</P
191 > - Matches any single character, e.g. <SPAN
229 > - The preceding character or expression is matched ZERO or ONE
252 > - The preceding character or expression is matched ONE or MORE
275 > - The preceding character or expression is matched ZERO or MORE
301 > character denotes that
302 the following character should be taken literally. This is used where one of the
303 special characters (e.g. <SPAN
306 >) needs to be taken literally and
307 not as a special meta-character. Example: <SPAN
309 >"example\.com"</SPAN
311 sure the period is recognized only as a period (and not expanded to its
312 meta-character meaning of any single character).
334 > - Characters enclosed in brackets will be matched if
335 any of the enclosed characters are encountered. For instance, <SPAN
339 matches any numeric digit (zero through nine). As an example, we can combine
343 > to match any digit one of more times: <SPAN
368 > - parentheses are used to group a sub-expression,
369 or multiple sub-expressions.
394 > character works like an
398 > conditional statement. A match is successful if the
399 sub-expression on either side of <SPAN
402 > matches. As an example:
405 >"/(this|that) example/"</SPAN
406 > uses grouping and the bar character
407 and would match either <SPAN
409 >"this example"</SPAN
423 > These are just some of the ones you are likely to use when matching URLs with
427 >, and is a long way from a definitive
428 list. This is enough to get us started with a few simple examples which may
429 be more illuminating:</P
441 that uses the common combination of <SPAN
448 denote any character, zero or more times. In other words, any string at all.
449 So we start with a literal forward slash, then our regular expression pattern
453 >) another literal forward slash, the string
457 >, another forward slash, and lastly another
462 a directory path here. This will match any file with the path that has a
463 directory named <SPAN
470 any characters, and this could conceivably be more forward slashes, so it
471 might expand into a much longer looking path. For example, this could match:
474 >"/eye/hate/spammers/banners/annoy_me_please.gif"</SPAN
478 >"/banners/annoying.html"</SPAN
479 >, or almost an infinite number of other
480 possible combinations, just so it has <SPAN
486 > And now something a little more complex:</P
494 >/.*/adv((er)?ts?|ertis(ing|ements?))?/</TT
498 We have several literal forward slashes again (<SPAN
502 building another expression that is a file path statement. We have another
506 >, so we are matching against any conceivable sub-path, just so
507 it matches our expression. The only true literal that <SPAN
514 > our pattern is <SPAN
518 the forward slashes. What comes after the <SPAN
522 interesting part. </P
527 > means the preceding expression (either a
528 literal character or anything grouped with <SPAN
532 can exist or not, since this means either zero or one match. So
535 >"((er)?ts?|ertis(ing|ements?))"</SPAN
536 > is optional, as are the
537 individual sub-expressions: <SPAN
543 >"(ing|ements?)"</SPAN
554 >. We have two of those. For instance,
557 >"(ing|ements?)"</SPAN
558 >, can expand to match either <SPAN
571 >. What is being done here, is an
572 attempt at matching as many variations of <SPAN
574 >"advertisement"</SPAN
576 similar, as possible. So this would expand to match just <SPAN
592 >"advertisement"</SPAN
596 >"advertisements"</SPAN
597 >. You get the idea. But it would not match
600 >"advertizements"</SPAN
604 >). We could fix that by
605 changing our regular expression to:
608 >"/.*/adv((er)?ts?|erti(s|z)(ing|ements?))?/"</SPAN
609 >, which would then match
618 >/.*/advert[0-9]+\.(gif|jpe?g)</TT
622 another path statement with forward slashes. Anything in the square brackets
626 > can be matched. This is using <SPAN
630 shorthand expression to mean any digit one through nine. It is the same as
634 >. So any digit matches. The <SPAN
638 means one or more of the preceding expression must be included. The preceding
639 expression here is what is in the square brackets -- in this case, any digit
640 one through nine. Then, at the end, we have a grouping: <SPAN
644 This includes a <SPAN
647 >, so this needs to match the expression on
648 either side of that bar character also. A simple <SPAN
651 > on one side, and the other
652 side will in turn match either <SPAN
662 > means the letter <SPAN
666 can be matched once or not at all. So we are building an expression here to
667 match image GIF or JPEG type image file. It must include the literal
671 >, then one or more digits, and a <SPAN
675 (which is now a literal, and not a special character, since it is escaped
679 >), and lastly either <SPAN
689 >. Some possible matches would
692 >"//advert1.jpg"</SPAN
696 >"/nasty/ads/advert1234.gif"</SPAN
700 >"/banners/from/hell/advert99.jpg"</SPAN
701 >. It would not match
705 > (no leading slash), or
708 >"/adverts232.jpg"</SPAN
709 > (the expression does not include an
715 >"/advert1.jsp"</SPAN
720 in the expression anywhere).</P
722 > We are barely scratching the surface of regular expressions here so that you
723 can understand the default <SPAN
727 configuration files, and maybe use this knowledge to customize your own
728 installation. There is much, much more that can be done with regular
729 expressions. Now that you know enough to get started, you can learn more on
732 > More reading on Perl Compatible Regular expressions:
734 HREF="http://perldoc.perl.org/perlre.html"
736 >http://perldoc.perl.org/perlre.html</A
739 > For information on regular expression based substitutions and their applications
740 in filters, please see the <A
741 HREF="filter-file.html"
742 >filter file tutorial</A
752 >14.2. Privoxy's Internal Pages</A
758 > proxies each requested
759 web page, it is easy for <SPAN
763 trap certain special URLs. In this way, we can talk directly to
768 configured, see how our rules are being applied, change these
769 rules and other configuration options, and even turn
773 > filtering off, all with
774 a web browser. </P
776 > The URLs listed below are the special ones that allow direct access
784 > must be running to access these. If
785 not, you will get a friendly error message. Internet access is not
804 HREF="http://config.privoxy.org/"
806 >http://config.privoxy.org/</A
811 > There is a shortcut: <A
816 doesn't provide a fall-back to a real page, in case the request is not
826 Show information about the current configuration, including viewing and
827 editing of actions files:
837 HREF="http://config.privoxy.org/show-status"
839 >http://config.privoxy.org/show-status</A
847 Show the source code version numbers:
857 HREF="http://config.privoxy.org/show-version"
859 >http://config.privoxy.org/show-version</A
867 Show the browser's request headers:
877 HREF="http://config.privoxy.org/show-request"
879 >http://config.privoxy.org/show-request</A
887 Show which actions apply to a URL and why:
897 HREF="http://config.privoxy.org/show-url-info"
899 >http://config.privoxy.org/show-url-info</A
907 Toggle Privoxy on or off. This feature can be turned off/on in the main
911 > file. When toggled <SPAN
918 continues to run, but only as a pass-through proxy, with no actions taking
929 HREF="http://config.privoxy.org/toggle"
931 >http://config.privoxy.org/toggle</A
936 > Short cuts. Turn off, then on:
946 HREF="http://config.privoxy.org/toggle?set=disable"
948 >http://config.privoxy.org/toggle?set=disable</A
960 HREF="http://config.privoxy.org/toggle?set=enable"
962 >http://config.privoxy.org/toggle?set=enable</A
970 > These may be bookmarked for quick reference. See next. </P
977 >14.2.1. Bookmarklets</A
980 > Below are some <SPAN
982 >"bookmarklets"</SPAN
983 > to allow you to easily access a
987 > version of some of <SPAN
991 special pages. They are designed for MS Internet Explorer, but should work
992 equally well in Netscape, Mozilla, and other browsers which support
993 JavaScript. They are designed to run directly from your bookmarks - not by
994 clicking the links below (although that should work for testing).</P
996 > To save them, right-click the link and choose <SPAN
998 >"Add to Favorites"</SPAN
1002 >"Add Bookmark"</SPAN
1003 > (Netscape). You will get a warning that
1006 >"may not be safe"</SPAN
1007 > - just click OK. Then you can run the
1008 Bookmarklet directly from your favorites/bookmarks. For even faster access,
1009 you can put them on the <SPAN
1012 > bar (IE) or the <SPAN
1016 > (Netscape), and run them with a single click. </P
1024 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());"
1026 >Privoxy - Enable</A
1033 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());"
1035 >Privoxy - Disable</A
1042 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());"
1044 >Privoxy - Toggle Privoxy</A
1045 > (Toggles between enabled and disabled)
1051 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());"
1053 >Privoxy- View Status</A
1060 HREF="javascript:void(window.open('http://config.privoxy.org/show-url-info?url='+escape(location.href),'Why').focus());"
1069 > Credit: The site which gave us the general idea for these bookmarklets is
1071 HREF="http://www.bookmarklets.com/"
1073 >www.bookmarklets.com</A
1075 have more information about bookmarklets. </P
1084 >14.3. Chain of Events</A
1087 > Let's take a quick look at how some of <SPAN
1091 core features are triggered, and the ensuing sequence of events when a web
1092 page is requested by your browser:</P
1099 > First, your web browser requests a web page. The browser knows to send
1100 the request to <SPAN
1103 >, which will in turn,
1104 relay the request to the remote web server after passing the following
1113 > traps any request for its own internal CGI
1118 >) and sends the CGI page back to the browser.
1126 > checks to see if the URL
1128 HREF="actions-file.html#BLOCK"
1134 so, the URL is then blocked, and the remote web server will not be contacted.
1136 HREF="actions-file.html#HANDLE-AS-IMAGE"
1139 >"+handle-as-image"</SPAN
1144 HREF="actions-file.html#HANDLE-AS-EMPTY-DOCUMENT"
1147 >"+handle-as-empty-document"</SPAN
1150 are then checked, and if there is no match, an
1154 > page is sent back to the browser. Otherwise, if
1155 it does match, an image is returned for the former, and an empty text
1156 document for the latter. The type of image would depend on the setting of
1158 HREF="actions-file.html#SET-IMAGE-BLOCKER"
1161 >"+set-image-blocker"</SPAN
1164 (blank, checkerboard pattern, or an HTTP redirect to an image elsewhere).
1169 > Untrusted URLs are blocked. If URLs are being added to the
1173 > file, then that is done.
1178 > If the URL pattern matches the <A
1179 HREF="actions-file.html#FAST-REDIRECTS"
1182 >"+fast-redirects"</SPAN
1185 it is then processed. Unwanted parts of the requested URL are stripped.
1190 > Now the rest of the client browser's request headers are processed. If any
1191 of these match any of the relevant actions (e.g. <A
1192 HREF="actions-file.html#HIDE-USER-AGENT"
1195 >"+hide-user-agent"</SPAN
1198 etc.), headers are suppressed or forged as determined by these actions and
1204 > Now the web server starts sending its response back (i.e. typically a web
1210 > First, the server headers are read and processed to determine, among other
1211 things, the MIME type (document type) and encoding. The headers are then
1212 filtered as determined by the
1214 HREF="actions-file.html#CRUNCH-INCOMING-COOKIES"
1217 >"+crunch-incoming-cookies"</SPAN
1221 HREF="actions-file.html#SESSION-COOKIES-ONLY"
1224 >"+session-cookies-only"</SPAN
1228 HREF="actions-file.html#DOWNGRADE-HTTP-VERSION"
1231 >"+downgrade-http-version"</SPAN
1240 HREF="actions-file.html#FILTER"
1247 HREF="actions-file.html#DEANIMATE-GIFS"
1250 >"+deanimate-gifs"</SPAN
1253 action applies (and the document type fits the action), the rest of the page is
1254 read into memory (up to a configurable limit). Then the filter rules (from
1258 > and any other filter files) are
1259 processed against the buffered content. Filters are applied in the order
1260 they are specified in one of the filter files. Animated GIFs, if present,
1261 are reduced to either the first or last frame, depending on the action
1262 setting.The entire page, which is now filtered, is then sent by
1266 > back to your browser.
1270 HREF="actions-file.html#FILTER"
1277 HREF="actions-file.html#DEANIMATE-GIFS"
1280 >"+deanimate-gifs"</SPAN
1286 > passes the raw data through
1287 to the client browser as it becomes available.
1292 > As the browser receives the now (possibly filtered) page content, it
1293 reads and then requests any URLs that may be embedded within the page
1294 source, e.g. ad images, stylesheets, JavaScript, other HTML documents (e.g.
1295 frames), sounds, etc. For each of these objects, the browser issues a
1296 separate request (this is easily viewable in <SPAN
1300 logs). And each such request is in turn processed just as above. Note that a
1301 complex web page will have many, many such embedded URLs. If these
1302 secondary requests are to a different server, then quite possibly a very
1303 differing set of actions is triggered.
1309 > NOTE: This is somewhat of a simplistic overview of what happens with each URL
1310 request. For the sake of brevity and simplicity, we have focused on
1314 > core features only.</P
1322 >14.4. Troubleshooting: Anatomy of an Action</A
1330 HREF="actions-file.html#ACTIONS"
1333 HREF="actions-file.html#FILTER"
1336 to any given URL can be complex, and not always so
1337 easy to understand what is happening. And sometimes we need to be able to
1348 doing. Especially, if something <SPAN
1352 is causing us a problem inadvertently. It can be a little daunting to look at
1353 the actions and filters files themselves, since they tend to be filled with
1355 HREF="appendix.html#REGEX"
1356 >regular expressions</A
1357 > whose consequences are not
1358 always so obvious. </P
1360 > One quick test to see if <SPAN
1363 > is causing a problem
1364 or not, is to disable it temporarily. This should be the first troubleshooting
1366 HREF="appendix.html#BOOKMARKLETS"
1367 >the Bookmarklets</A
1368 > section on a quick
1369 and easy way to do this (be sure to flush caches afterward!). Looking at the
1370 logs is a good idea too. (Note that both the toggle feature and logging are
1374 > file settings, and may need to be
1380 > Another easy troubleshooting step to try is if you have done any
1381 customization of your installation, revert back to the installed
1382 defaults and see if that helps. There are times the developers get complaints
1383 about one thing or another, and the problem is more related to a customized
1384 configuration issue.</P
1391 HREF="http://config.privoxy.org/show-url-info"
1393 >http://config.privoxy.org/show-url-info</A
1395 page that can show us very specifically how <SPAN
1399 are being applied to any given URL. This is a big help for troubleshooting.</P
1401 > First, enter one URL (or partial URL) at the prompt, and then
1406 how the current configuration will handle it. This will not
1407 help with filtering effects (i.e. the <A
1408 HREF="actions-file.html#FILTER"
1414 one of the filter files since this is handled very
1415 differently and not so easy to trap! It also will not tell you about any other
1416 URLs that may be embedded within the URL you are testing. For instance, images
1417 such as ads are expressed as URLs within the raw page source of HTML pages. So
1418 you will only get info for the actual URL that is pasted into the prompt area
1419 -- not any sub-URLs. If you want to know about embedded URLs like ads, you
1420 will have to dig those out of the HTML source. Use your browser's <SPAN
1424 > option for this. Or right click on the ad, and grab the
1427 > Let's try an example, <A
1428 HREF="http://google.com"
1432 and look at it one section at a time in a sample configuration (your real
1433 configuration may vary):</P
1443 > Matches for http://www.google.com:
1445 In file: default.action <SPAN
1453 {+change-x-forwarded-for{block}
1454 +deanimate-gifs {last}
1455 +fast-redirects {check-decoded-url}
1456 +filter {refresh-tags}
1457 +filter {img-reorder}
1458 +filter {banners-by-size}
1460 +filter {jumping-windows}
1461 +filter {ie-exploits}
1462 +hide-from-header {block}
1463 +hide-referrer {forge}
1464 +session-cookies-only
1465 +set-image-blocker {pattern}
1468 { -session-cookies-only }
1474 In file: user.action <SPAN
1481 (no matches in this file) </PRE
1487 > This is telling us how we have defined our
1489 HREF="actions-file.html#ACTIONS"
1495 which ones match for our test case, <SPAN
1499 Displayed is all the actions that are available to us. Remember,
1503 > sign denotes <SPAN
1513 >. So some are <SPAN
1520 >. Each example we try may provide a slightly different
1521 end result, depending on our configuration directives.</P
1527 > file. The large, multi-line
1528 listing, is how the actions are set to match for all URLs, i.e. our default
1529 settings. If you look at your <SPAN
1532 > file, this would be the
1533 section just below the <SPAN
1536 > section near the top. This
1537 will apply to all URLs as signified by the single forward slash at the end
1538 of the listing -- <SPAN
1543 > But we have defined additional actions that would be exceptions to these general
1544 rules, and then we list specific URLs (or patterns) that these exceptions
1545 would apply to. Last match wins. Just below this then are two explicit
1548 >".google.com"</SPAN
1549 >. The first is negating our previous
1550 cookie setting, which was for <A
1551 HREF="actions-file.html#SESSION-COOKIES-ONLY"
1554 >"+session-cookies-only"</SPAN
1557 (i.e. not persistent). So we will allow persistent cookies for google, at
1558 least that is how it is in this example. The second turns
1566 HREF="actions-file.html#FAST-REDIRECTS"
1569 >"+fast-redirects"</SPAN
1572 action, allowing this to take place unmolested. Note that there is a leading
1575 >".google.com"</SPAN
1576 >. This will match any hosts and
1577 sub-domains, in the google.com domain also, such as
1580 >"www.google.com"</SPAN
1583 >"mail.google.com"</SPAN
1587 >"www.google.de"</SPAN
1588 >! So, apparently, we have these two actions
1589 defined as exceptions to the general rules at the top somewhere in the lower
1597 > is referenced somewhere in these latter sections.</P
1602 > file, we again have no hits.
1603 So there is nothing google-specific that we might have added to our own, local
1604 configuration. If there was, those actions would over-rule any actions from
1605 previously processed files, such as <TT
1612 > typically has the last word. This is the
1613 best place to put hard and fast exceptions,</P
1615 > And finally we pull it all together in the bottom section and summarize how
1619 > is applying all its <SPAN
1636 > Final results:
1640 +change-x-forwarded-for{block}
1641 -client-header-filter{hide-tor-exit-notation}
1642 -content-type-overwrite
1643 -crunch-client-header
1644 -crunch-if-none-match
1645 -crunch-incoming-cookies
1646 -crunch-outgoing-cookies
1647 -crunch-server-header
1648 +deanimate-gifs {last}
1649 -downgrade-http-version
1652 -filter {content-cookies}
1653 -filter {all-popups}
1654 -filter {banners-by-link}
1655 -filter {tiny-textforms}
1656 -filter {frameset-borders}
1657 -filter {demoronizer}
1658 -filter {shockwave-flash}
1659 -filter {quicktime-kioskmode}
1661 -filter {crude-parental}
1662 -filter {site-specifics}
1663 -filter {js-annoyances}
1664 -filter {html-annoyances}
1665 +filter {refresh-tags}
1666 -filter {unsolicited-popups}
1667 +filter {img-reorder}
1668 +filter {banners-by-size}
1670 +filter {jumping-windows}
1671 +filter {ie-exploits}
1678 -handle-as-empty-document
1680 -hide-accept-language
1681 -hide-content-disposition
1682 +hide-from-header {block}
1683 -hide-if-modified-since
1684 +hide-referrer {forge}
1687 -overwrite-last-modified
1688 -prevent-compression
1690 -server-header-filter{xml-to-html}
1691 -server-header-filter{html-to-xml}
1692 -session-cookies-only
1693 +set-image-blocker {pattern} </PRE
1699 > Notice the only difference here to the previous listing, is to
1702 >"fast-redirects"</SPAN
1705 >"session-cookies-only"</SPAN
1707 which are activated specifically for this site in our configuration,
1708 and thus show in the <SPAN
1710 >"Final Results"</SPAN
1713 > Now another example, <SPAN
1715 >"ad.doubleclick.net"</SPAN
1726 > { +block{Domains starts with "ad"} }
1729 { +block{Domain contains "ad"} }
1732 { +block{Doubleclick banner server} +handle-as-image }
1733 .[a-vx-z]*.doubleclick.net</PRE
1739 > We'll just show the interesting part here - the explicit matches. It is
1740 matched three different times. Two <SPAN
1746 >"+block{} +handle-as-image"</SPAN
1748 which is the expanded form of one of our aliases that had been defined as:
1751 >"+block-as-image"</SPAN
1753 HREF="actions-file.html#ALIASES"
1759 the first section of the actions file and typically used to combine more
1760 than one action.)</P
1762 > Any one of these would have done the trick and blocked this as an unwanted
1763 image. This is unnecessarily redundant since the last case effectively
1764 would also cover the first. No point in taking chances with these guys
1765 though ;-) Note that if you want an ad or obnoxious
1766 URL to be invisible, it should be defined as <SPAN
1768 >"ad.doubleclick.net"</SPAN
1770 is done here -- as both a <A
1771 HREF="actions-file.html#BLOCK"
1785 HREF="actions-file.html#HANDLE-AS-IMAGE"
1788 >"+handle-as-image"</SPAN
1791 The custom alias <SPAN
1795 >+block-as-image</TT
1798 simplifies the process and make it more readable.</P
1800 > One last example. Let's try <SPAN
1802 >"http://www.example.net/adsl/HOWTO/"</SPAN
1804 This one is giving us problems. We are getting a blank page. Hmmm ...</P
1814 > Matches for http://www.example.net/adsl/HOWTO/:
1816 In file: default.action <SPAN
1826 +change-x-forwarded-for{block}
1827 -client-header-filter{hide-tor-exit-notation}
1828 -content-type-overwrite
1829 -crunch-client-header
1830 -crunch-if-none-match
1831 -crunch-incoming-cookies
1832 -crunch-outgoing-cookies
1833 -crunch-server-header
1835 -downgrade-http-version
1836 +fast-redirects {check-decoded-url}
1838 -filter {content-cookies}
1839 -filter {all-popups}
1840 -filter {banners-by-link}
1841 -filter {tiny-textforms}
1842 -filter {frameset-borders}
1843 -filter {demoronizer}
1844 -filter {shockwave-flash}
1845 -filter {quicktime-kioskmode}
1847 -filter {crude-parental}
1848 -filter {site-specifics}
1849 -filter {js-annoyances}
1850 -filter {html-annoyances}
1851 +filter {refresh-tags}
1852 -filter {unsolicited-popups}
1853 +filter {img-reorder}
1854 +filter {banners-by-size}
1856 +filter {jumping-windows}
1857 +filter {ie-exploits}
1864 -handle-as-empty-document
1866 -hide-accept-language
1867 -hide-content-disposition
1868 +hide-from-header{block}
1869 +hide-referer{forge}
1871 -overwrite-last-modified
1872 +prevent-compression
1874 -server-header-filter{xml-to-html}
1875 -server-header-filter{html-to-xml}
1876 +session-cookies-only
1877 +set-image-blocker{blank} }
1880 { +block{Path contains "ads".} +handle-as-image }
1894 configuration! But we did not want this at all! Now we see why we get the
1895 blank page. It is actually triggering two different actions here, and
1896 the effects are aggregated so that the URL is blocked, and <SPAN
1900 to treat the block as if it were an image. But this is, of course, all wrong.
1901 We could now add a new action below this (or better in our own
1905 > file) that explicitly
1914 HREF="actions-file.html#BLOCK"
1923 > in them (remember, last match in the configuration
1924 wins). There are various ways to handle such exceptions. Example:</P
1941 > Now the page displays ;-)
1942 Remember to flush your browser's caches when making these kinds of changes to
1943 your configuration to insure that you get a freshly delivered page! Or, try
1949 > But now what about a situation where we get no explicit matches like
1960 > { +block{Path starts with "ads".} +handle-as-image }
1967 > That actually was very helpful and pointed us quickly to where the problem
1968 was. If you don't get this kind of match, then it means one of the default
1969 rules in the first section of <TT
1973 the problem. This would require some guesswork, and maybe a little trial and
1974 error to isolate the offending rule. One likely cause would be one of the
1976 HREF="actions-file.html#FILTER"
1982 These tend to be harder to troubleshoot.
1983 Try adding the URL for the site to one of aliases that turn off
1985 HREF="actions-file.html#FILTER"
2002 .worldpay.com # for quietpc.com
2025 >{ -filter -session-cookies-only }</TT
2028 Or you could do your own exception to negate filtering: </P
2039 # Disable ALL filter actions for sites in this section
2048 > This would turn off all filtering for these sites. This is best
2053 exceptions. Note that when a simple domain pattern is used by itself (without
2054 the subsequent path portion), all sub-pages within that domain are included
2055 automatically in the scope of the action.</P
2057 > Images that are inexplicably being blocked, may well be hitting the
2059 HREF="actions-file.html#FILTER-BANNERS-BY-SIZE"
2062 >"+filter{banners-by-size}"</SPAN
2066 that images of certain sizes are ad banners (works well
2071 >most of the time</I
2073 > since these tend to be standardized).</P
2081 > is an alias that disables most
2082 actions that are the most likely to cause trouble. This can be used as a
2083 last resort for problem sites. </P
2094 # Handle with care: easy to break
2096 mybank.example.com</PRE
2106 >Remember to flush caches!</I
2112 > reference lacks the TLD portion (e.g.
2116 >). This will effectively match any TLD with
2120 > in it, such as <TT
2122 >mail.google.de.</TT
2124 just as an example.</P
2127 If this still does not work, you will have to go through the remaining
2128 actions one by one to find which one(s) is causing the problem.</P
2136 SUMMARY="Footer navigation table"