: That's a good question, I'm glad you asked. It's almost a shame that given all the possibilities CSS offers in designing a website that a table-based layout is still the most emulated. But, still, it does have its advantages and can be one of the harder things for a beginner to CSS to master.
There are in fact several different ways to create a three column table, and there is no "right or wrong." There are advantages (and disadvantages) to all methods; floats, relative positioning, absolute positioning, etc. Rather than discuss in detail all the possiblities, I present to you a link to the (in)famous css-discuss website.
This link leads you to an expanding collection of three column layout templates, each explaining the different methods involved and, in most cases, providing a walkthrough of both the HTML and the CSS. Hopefully it will help you find a method that works for you and your site!