Attack of the little green links.
 

I've noticed something strange in the last week or two. As I surf the web many of the sites I visit are laced with double-underline hyperlinks for common words. At first I thought it was just interal links on related words. Wikipedia does this for example. However after I started looking at the actual links it's fairly clear there is a marketing plan involved here.

Anyone know where these come from?

A programmer

Spyware or a program you downloaded and didn't uncheck the option to underline the links. Trillian does this too. Go check the preferences of anything you recently installed, and if you didn't knowingly install something run an anti-spyware program.

Specifically, that sounds like Ezula's Top Text. If none of the free adware removers pull it out, here are manual removal instructions

I've done a bit of digging. I'm fairly compulsive about spyware scanning so as I suspected, it's not on my PC. It's on the sites themselves. For example you can see it here Notice the double underlines?

A stroll through their HTML code turned up something called intelliTxt

The web abounds with comments on intelliTxt.

There is also a note about how intellitxt is often taken to be Top Text (nice call GD).

I can't see any double underlines at that site.. I'm viewing this on a Mac with Mozilla, though.

The are in the text towards the bottom of the page. Wierd, but it is a marketing gimik.

Wow, that could be the first good argument I've heard for using a Mac in err umm well ever. :)

Now that I'm on a PC, I see them. Definitely weren't there before.

Yep. It's a new advertising technique. Experts Exchange has been using them for a while. Like a twisted version of Ad Words.