Milo, thanks for the answer. I removed the <form> in TEST2.asp and the javascript of TEST1.asp works inside the tooltip, the form in TEST1.asp can be submitted.
Three questions still.
1. Though the form in TEST1.asp can be submitted, but the tooltip disappear at the same time, and the result is posted back to the same page. I would like to see the result in the tooltip, how to do it?
2. Is it really a case of multiple <form>? Actually each individual program contains 1 <form> only. If I just simply use javascript window.open('TEST1.asp) to call TEST1.asp in a pop-up window, the form can be submitted and the result is displayed inside the pop-up window.
3. I think it is common that an application calls another program e.g. I have a small program, say "CheckUser.asp" that asks user to enter ID and password, then validates with the user database and posted back whether the user id valid. "CheckUser.asp" contains a <form> obviously. In the main application e.g. "StockQuote.asp" which contains a <form> for user to enter stock number, stock chart type. If user selects some special options within the form, I use the tooltip.ajax to call the "CheckUser.asp" to validate the user identity first before the user can proceed. It seems tooltip.ajax does not return the beaviour as expected because the 2 programs "CheckUser.asp" and "StockQuote.asp" contains a <form>.