>>>Thank you for the link to jquery docs. I will go and read. But what I don't understand (and I am sure it is obvious to you) is what specifically jquery does for me. Say I want the application be a simple data entry form (bunch of text boxes and drop down controls and a Submit button). I don't understand service JQuery provides in this case.
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>>for starters make sure that your code runs on any browser, not just IE9, but IE6 ad well and FF, Chrome and so on...
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>I agree. Thanks.

You might skip IE6. It is seriously lacking in standards support and is seriously old, and it is not widely used at all. Designing for it will give you far more headaches than it is worth.

We do asp.net web applications that people use in iPads all the time. Very little needs to be done to make them work fine in the iPad browser (they don't look like an Apple app, but they work).

If you get down to an iPhone, all bets are off. You are better doing an IOS app at that point (which is something I will not lower myself to do).