Hello Link :)
There are a few ways to do this. Before, in the olde years of web designnne, we used tables to hack together a position. I still resort to tables when I am desperate nowadays, but the best and proper way to do positioning is through divs and positioning them with CSS.
This site gives a great overview of the concept, so I won’t repeat it here.
Learn how the box model works is the first step. The next step is to fire Notepad up and test test test with simple test code like this.
Since some of the differences in browser errors in rendering, inconsistencies etc, has to do with different interpretations of the box model, be sure to test in the range of IEs (6, 7, and 8) as well as Firefox. With simple positioning, there should be no problems though.
This will likely be covered well in any beginner’s CSS book. I advise you to pick one up. Again, the best way to learn code is to DO code, so dig in and position those divs!
If you want to see how Fluther’s design works, save a copy of the page to your local machine and start gutting it out. Replace all the text with “blah blah blah”. Look at the css behind it. Change some colors to figure out where you are. Strip it down till you have the basic framework and cut all the bloat code from it, then learn from that. Nothing’s better than getting your hands messy with code cruft!