Hey all,
some of you know me from some of my earlier questions with my css stuff.

I recently interviewed for a position for a company who uses ajax. All their AJAX stuff is already built, so, they aren't going to require me to mess with it much at first, most of it will be what I already know, XHTML, PHP, MySQL, CSS, some CGI (it's an old program obviously).

Because, eventually, I will end up working with their AJAX stuff, I need to make sure that I can get a handle on it some.

I did buy a reference book, but, there are some things that are not really answered, from a beginner perspective at least.

I get the sense that most everything happens client side (browser), but what limitations are placed on AJAX usage from the server? Is there a way to check and see what my server can and can't allow?

Is there any way to make sure that everything I do will be able to be used by folks with IE6, IE7 and Firefox?

The last thing is, are there any great online tutes that can help me with storing the user's actions within my AJAX stuff into a database?

As a for instance, let's say I am offering a user their own page. In this page they can move the links around or the text or whatever. How would I save the end result in such a way that everyone who comes to the page will see it the way that the page owner has changed it.

Any thoughts on where to find this kind of information?
Thanks
Sage