I'm not sure I follow.
CSS is a way of formatting HTML, not a replacement for it.
There are two schools of thought on crateing web page payouts in your HTML document:
1) Table Based layouts
2) CSS layouts.
the advantage of a CSS Layout is that the page information is removed from the layout components.
CSS adds styles to div tags to control the layout rather than using tables.
There really is no easy conversion to move from a table based layout to a CSS based layout. To move to a CSS based layout, you basically need to recreate the page from scratch.