Please, do NOT do what Kerplunk suggests. Using tables for design purposes is not only semantically wrong, it's also soo 1999.
Learn CSS. Follow the defined standards from the W3C:
http://www.w3.org/Style/CSS/
Opera and Firefox will render pages very well with the defined standards. IE is a tough git that sometimes takes a little bit of messing with to get it right. Sometimes it can be acheived with standard code, other times you may have to employ a CSS 'hack' if you want to get your way.
Importantly, make your page elements a percentage width of the screen, not set pixel sizes. Same with the font sizes. So it will still look half-decent with larger screen resolutions. This is sometimes known as a 'liquid' design.
http://www.thenoodleincident.com/