Many blogs and web sites have been displaying ads in what I find is an annoying fashion. Selected words are underlined twice in green. When you run your mouse over them, an annoying popup appears, advertising something. Here's a random example.
(My favorite was a blog which had a phrase something like "overall this method works well," where overall was underlined and offered to sell me blue jeans with bibs.)
There outta be ways to block these things, and there are in fact many. These popups all have the name IntelliTXT on them, someplace. They are so ubiquitous that Firefox 2.0's Google search offers 11 different versions of the string "IntelliTXT *", most of which have to do with blocking, removing, or disabling the things.
As it turns out, Wikipedia has a good "stub" article, which includes blocking information. In my case, the easiest way to block everything is to use the Adblock extension for Firefox. Just add the string "*Intellitxt*" to Adblock's filter, reload the offending page, and the double green lines are gone.
Wikipedia: It's not just for truthiness.