Personally i use percentages and pixels for my layouts only because i have never really gotten the grasp of ems. 2 column layouts are going to be your best bet starting out, they're easier to code and they still look good. No matter what you do though with css you're always going to run into problems with Internet Explorer, its a crap browser that all Windows users have and 75% of the people who run windows use IE so sometimes you're going to have to find the hacks for ie and make ie specific style sheets... Every designer should know how to make their sites cross browser compatible, it sucks but we have to do it to prove our skills