Using Diigo (social annotation tool) to highlight links you've already visited

I've got a few pages listing links that I want to read through (currently, Danah Boyd's articles on social networking, Douglas Crockford's Javascript articles, some links on Catholic evangelism, and Brian McCallister's API design references).

The problem is that I'm often not sure which links I've already visited.

So I'm now using a browser extension called Diigo that lets me highlight text on the page (e.g. the links I've already visited). Seems to work pretty well - when I come back to these pages, my highlighting is shown in yellow. It got a good review on TechCrunch.