CSS centering an unorded list menu + screen resolutions

hmm ok,

I created an undorded list drop down menu in css using instructions here (The No-Code Way to a Pure CSS Horizontal Drop-Down Menu with Expression Web) and it works fine, but because of the huge variance of screen resolutions people use i would really like it to be centered, after literally spending hours and hours searching the net i find most sites seem to say it cant be done, others say it can but i haven't found one that works with a drop down with an unordered list css drop down menu.

any idea's ?

Also what are people doing about the huge variance of screen resolutions that people use to view a website? I have found that even if i use percentages for width etc the text still becomes so small as to be unreadable, what resolution should I be basing my website on? because apart from getting the resolution of the user (or god forbid changing their resolution,) the alternative seems to be loading a different version of the page that displays well at that resolution what are the alternatives?

Ok and yes i am a newbie to all this css stuff, the last website i ever did was years ago, hand coded in notepad when the max resolution was 800x600.

rgds
syb