You should design for Firefox. Far less people use Safari.
Is this an image that's changing colours, or a cell with a coloured background?
EDIT: Ok it appears to be one big image. Is that a good idea? :o
Do you NEED to learn HTML? Or do you just want to make a website?
I recommend using WYSIWYG at first, and learning how to code by looking at your code. It's pretty obvious.
I don't understand your problem either, but it's likely that you're trying to do something unnecessarily complicated. If you provide more info, we can dig into your actual problem though.
I always question whether it's necessary for newbies to learn CSS. Sure it's better, but setting up your first website is a big hurdle to get over.
Others may disagree, but I'd just stick to plain old-fashioned tables at first.