AJAX Extenders are not working

Question

I have downloaded the AJAX control tool kit from the asp.net website.
I am working on Visual Studios 2008.
After adding the extender for any control for e.g button extender like confirm....and adding the code as mentioned in the the pdfs from the ASp.net website....the message box is not displayed....
I have added the script manager on my page.....but still no outcome
pls help......