Well, you should not confuse what CSS and DIVs do to your code. Try this. Remove all from <style> to </style> and also all the style="bla bla bla" and see what happens.
DIVs are containers to group together part of the content of a page so you can give it color, format, etc. And that's what CSS is used for.
For example, to gruoup a few things this would be enough
<div><img src="picture.jpg" />this is my picture</div>
and this would paint the text in red
<div style="color: #f00"><img src="picture.jpg" />this is my picture</div>
Hope this helps.