Respected All

I am working on VS 2005 using VB. I develop small website for trial base. I want to use AJAX in my Website. I understood xmlHTTPRequest object and other DOM object but still I can't apply AJAX in my site. like, How to write code for Dropdown list control using AJAX? Pl Help me to do.

2nd thing that, i understood about webservices and create webmethod also but still i am not able to use webservice in real application/website. pl help me on both topic.

If possible, pl send example with source.

waiting your positive replay.