Some of these layouts are based on positioning schemes, which you explored in Positioning, Floats, and Z-index. Some of the layouts use floats, which, you'll recall, are not a positioning scheme but do enable you to create columnar layouts. The combination of floating and positioning is common as well, and you'll get to see examples of that in action.
For the purposes of clarity, I'm going to teach you how to create these designs in their most pure form. This means that I'm leaving out a number of popular hacks that might be necessary for you to implement, depending upon your browser base. Without the hacks, these designs will work very well in the browsers described in this table.
Browser Support for CSS Layouts in This tutorial
Browser OS Version ------------------------------------------------ Internet Explorer Windows 6.0 Mozilla All Available 1.x+ Netscape All Available 6.x Firefox All Available All Opera All Available 6.x Safari Macintosh 1.x+
All contemporary browsers in use will have no trouble with these layouts. The need for hacks or workarounds comes in when you have to support browsers outside this list, particularly Internet Explorer versions 5.0 and 5.5 for Windows, all IE versions for Macintosh, and Netscape earlier than 6.0; all have incorrect or partial implementation of the portions of CSS required.