Slashdot recently reported that Firefox is improving it's pop-up blocking by defaulting options to not allow plug-ins like Macromedia Flash or Java to launch pop-ups. This change is coming after more and more advertisers are using plug-ins to launch unrequested pop-ups.

The ability for Firefox to stop these pop-ups has long existed, but the option wasn't default because it blocks requested pop-ups as well. It's easy for the browser to identify pop-ups that spawn from JavaScript code (the most common method) because they launch from events that the browser can easily identify because the browser execute all the JavaScript commands itself. Unrequested JavaScript events are event a user can't really avoid while browsing like "onload" (when you enter a web page) or "onunload" (when you leave a web page). Requested events are ones like "onclick" (when you click an object - like a link or image).

Apparently its harder to distinguish events that take place within a plug-in because the plug-in is a completely separate program running within the space of the browser - and the plug-in may not communicate back to the browser whats taking place within the plug-in. So Firefox can't tell if a new window launched from within a plug-in was requested or not.

The Firefox developers are definitely concerned about this situation, they don't want you to not get your requested pop-ups (this is a really annoying situation if you are ever put in it), so they are working on finding a solid solution before implementing it into the browser for public consumption.

If you want to be ahead of the pack, you can currently download an extension released by the Firefox team that will block all pop-ups (and pop-unders) from plug-ins aptly named "Pop-ups Must Die!" Be warned however that this is a test and as of current this may break requested pop-ups from plug-ins as well. But there is a work around, you just have to white-list the web site and it will be allowed access to spawn pop-ups.

I am currently having one problem though. On my Mac running Firefox 1.0.2 and with the Pop-ups Must Die! extension I get warned that a pop-up was blocked and I am given the option to allow the pop-up or white-list the web site. But on my Windows also running Firefox 1.0.2 with the extension installed on the same page I do not get the warning. So be prepared for possible buggy results while this is a work in progress for the Firefox team.

You can follow along in Mozilla employee Asa Dotzler's blog here and here.