Pls advise if its easier to use Divs or Tables to do such a layout. I've been told tables are less problematic? Since they've been around for a long time and the layout has to look the same even in IE 6.
In general that's a "debate" that died a long time ago.. with the exception of HTML emails, where CSS still holds no decent ground.
However, you say you are stuck with OSCommerce... my apologies. I took a look at that a few months ago and almost died. : (
if we can't use html to beautify the website? how are we supposed to do it then?
Ideally not with HTML but obviously you have specific constraints. Normalyl we use CSS but if you're good, you use the natural flow and default behaviours as much as possible. Let rocks roll down the hill themselves if they gotta be at the bottom.
IE Developer Toolbar is the only tool I know of, and it's not as useful as Firebug.
However editing CSS on the fly, I've always done by having the page open in my browsers, the page and CSS files are on the server and an open ftp connection, I make a change in the open CSS file, save, and f5 my browsers. The change appears immediately.
I can't really tell from a diagram what the page is supposed to do.