Divs are used to create sections of your page, including the header, left column, content, right column, and footer. We also sometimes throw in a few other divs to better organize the structure of a page. The trick to organizing the divs is the float property. When you float a div it floats the specified direction. We use floats to create columns. Just remember to clear your floats.
float:left; or float:right;
All following items (divs) flow next to the floated div.
The following sub-assignments will help you understand this process:
Regarding resets, read the following article and use the normalize.css reset.