In general, unless you pick a particular IDE style environment like Dreamweaver or Microsoft Expression Web, you will mainly be working with source files and you won't really have much contact with the higher level stuff like AJAX through the tool. You can create anything you like but you will have to navigate the higher level concepts on your own.
I'm just saying that most web tools tend to look like glorified text editors with support for language syntax (HTML, Javascript, and CSS.) The commercial tools are where the integration with more elaborate functionality happens.
CSS would be particularly tough to pick up by relying on a tool. You pretty much have to tough it out and learn how it works hands on.
I highly recommend that you try Firefox with the Firebug web developer add-on. For my money (actually time), Firebug offers the most punch in terms of learning. Firebug allows you to experiment directly with CSS in real time and see the effects of changes interactively.