Filter Rules: Using the "always allow" rule
The "always allow" filter rule is a highly specialized rule whose only job is to override the exclusionary filter rules "deny" and "requires approval".
An example of using the "always allow" rule would be:
A "deny" filter rule is created to exclude any URL with both "sex" and "porn" in it.
A less restrictive "require approval" filter rule is used to single out any URL with only "sex" in it.
The webmaster finds that, with each rebuild of the index, the URL http://dir.yahoo.com/Entertainment/Humor/Sex/ is singled out for approval. The webmaster trusts Yahoo and so he adds the URL to the "Always Allow Pages". This URL will never again be affected by exclusionary filters, but the filters will continue to do good work in weeding out other files.
If a web page is affected by both "always allow" and "deny" rules, then it will be allowed.
If a web page is affected by both "always allow" and "require approval" rules, then it will be allowed.
The "always allow" rule does not interfere with the "promote", "no update on redirect", "index nofollow" or "follow noindex" rules.
It is best to not have very general strings in an "always allow" rule. The "always allow" rule is quite effective at overruling the "deny" rules, which form the basis for features like the "Forbid Sites" rule. Oftentimes when customers report that they've tried to delete a URL and yet it continues to be added to their index, it is because there is an "always allow" rule which applies to their entire site and is masking the "forbid sites" rule.
Always allow rules can contain specific URL's and hostnames with valid content, while deny or require approval rules can focus more on the document text. Any always allow rule, whether focused on hostname, URL, or document text, will override any exclusionary rule, no matter what part of the record it is focused on.
"Filter Rules: Using the "always allow" rule" https://www.xav.com/scripts/search/help/1127.html