I had the same problem, which I solved by adding the following to my user style (using Stylish): @namespace url(http://www.w3.org/1999/xhtml); @-moz-doc

I had the same problem, which I solved by adding the following to my user style (using Stylish): @namespace url(http://www.w3.org/1999/xhtml); @-moz-document domain("news.ycombinator.com") { .title > :visited, .subtext > a[href*="item?id"]:visited { color: #ff6600 !important; } } It marks visited links / comment threads in orange. I use Firefox but think you can do something similar for Chrome.