As Ralph says, you'll need to give us more of a clue. It looks pretty much the same for me in Firefox, Chrome, IE and Opera - those links start off mid-green and turn dark green when clicked on. In most browsers the :visited links have fractionally smaller text.
Any posts I write in Arial are on my mobile phone, so please excuse typos etc. Any posts I write in Verdana are on a PC, so feel free to berate me mercilessly for any mistakes
noslenwerd, make sure to refresh your browser / clear the cache etc. Sometimes the browser uses the old version of the style sheet that it copied last time. Another option is to rename the style sheet (at least for testing purposes) to force the browser to reload it.