No problem. Well, these types of more complicated layout issues (not to mention with a tricky javacript animation) tend to be a little hard to explain over a forum, especially if you aren't already really familiar with basic html and css.
At this point I highly recommend at least going through the w3schools tutorials (start with HTML then CSS): www.w3schools.com/
I mean I'm a big fan of just diving into things but as it turns out, with web development it's actually quite tricky if you aren't familiar with the basics and general theory of it (which you can't really get by diving in). That doesn't mean you don't still have to dive in... and of course the challenges never end...
I should mention that I now see two problems with your design. One that already pointed out, the design has no vertical flexibility. You could always add scroll bars, but the website will appear tiny on larger screens. Probably a bigger issue (unless you don't care about IE6, I do but some don't anymore) is the transparent PNG. It's not going to be transparent on that browser or older.
So moving ahead, after using Firebug to look more closely at your code, my suggestion once again is to put all of your content for each "page" into a single DIV. By content I mean all of the text and accompanying graphics (not background) from each "page". Right now you have multiple divs but you only need one (per page) unless the page has a tricky layout. And now I'm thinking an absolute div would be a lot easier. So make it absolute...
You don't actually need to "center" it. Just give it a width that's no bigger than the inside of the shoelace area (a little thinner for breathing room). To give the illusion of it being centered, you would use the "left" and "top" properties like:
overflow: auto; (this last one will add the scrollbars if (only if) needed.
Lastly, you'd need to assign position: relative;
to the parent div
(the one that has the background). Position: relative will make the top left of the background be the "zero point" or the starting point for the content (absolute) div (otherwise it would start from the top-left of the screen).
As far as the animation, I'm not sure I understand what you're trying to do so that's going to a tougher thing to help with. But my instructions shouldn't mess it up.
Let me know if you can get it to work!