Oh ! Thanks for correction ! I was heavily shocked & surprised while reading first reply ! :)
Actually, I am developing an iGoogle Gadget that will access the spreadsheet data & allow to write back to it. One thing to ask here that, gdata is available for Calender as shown on the above link you have provided. However, the spreadsheet API provides Protocol service to access its feeds. Here, the question is that, google doesn't support cross-browser communication. So, to write back to spreadsheet, I cannot send ajax request. Then, as per it given in Google Documentation, if I want to send PUT request after user authorization, ( http://code.google.com/apis/spreadsheets/data/3.0/developers_guide.html#UpdatingCells), how will it be possible ? Or In the sense, will I be able to send AJAX request after granting access by user ?
