''website I visit frequently causes an adult site to pop up in the background'' Installing "Adblock Plus" (ADP) with filter subscriptions of "EasyList US" would probably stop a gambling site. Most unwanted pop-ups now are JavaScript and the pop-up blockers built into browsers are ineffective against such pop-ups. Adblock Plus will do nothing by itself without filters, and you can create you own filters. When you install an extension always visit the author's home page. * Adblock Plus :: Add-ons for Firefox (608.3 KB)<br>https://addons.mozilla.org/firefox/addon/adblock-plus/ * Adblock Plus — for annoyance-free web surfing<br>http://adblockplus.org/en/ A nice feature of Adblock Plus filters is that each subscription, and your own additions are maintained separately. Another is that you can bring up a "blockable items" report to see what can be blocked as well as what is blocked, and you can see the specific filter that is blocking an item, and mousing over the filter will tell you which subscription it is in. If you look at the blockable list you may not see the gambling site, because it is already blocked by blocking a JavaScript script (.js) file. Such files that are not needed and only bring in unwanted ads will be be blocked if known. You can use the blockable list to create your own filter to block a site listed. [https://addons.mozilla.org/firefox/addon/blocksite/ BlockSite] is another useful extension, which automagically blocks websites of your choice. Additionally, this extension will '''disable all hyperlinks to these websites''', by just displaying the link text without the clicking functionality. Especially useful on search results lists to prevent you from clicking on something you already know you don't want to go to. <br><small>Please mark "Solved" one answer that will best help others with a similar problem -- hope this was it.</small> ---- * Adblock - MozillaZine Knowledge Base<br>http://kb.mozillazine.org/Adblock * Blocking bad sites and annoyances - MozillaZine Knowledge Base<br>http://kb.mozillazine.org/Blocking_bad_sites_and_annoyances * Blocking sites - MozillaZine Knowledge Base<br>http://kb.mozillazine.org/Blocking_sites

Use these add-ons in Conjunction: -> Adblock Plus 1.3.9 * https://addons.mozilla.org/en-US/firefox/addon/adblock-plus/ * Subscribe to Filter lists ** http://adblockplus.org/en/subscriptions ** http://adblockplus.org/en/getting_started -> Adblock Plus Pop-up Addon 0.2.8 * https://addons.mozilla.org/en-US/firefox/addon/adblock-plus-pop-up-addon/ Check and tell if its working.