Adding httphandler in Web.config file

Hi,

I am new to asp.net

I have a created a new project & a new form containing a ScriptManager,
Updatepanel, Textbox, Button.
When I execute this page, the button click event fires. But in the status
bar , a warning message gets displayed. The messsage was 'sys is not
defined'. I viewed the source of the page.The error statement is -
Sys.WebForms.PageRequestManager._initialize('ScriptManager1',
document.getElementById('form1'));

So I added an httphandler in Web.config file to fix the error in the status
bar.
The httphandler added is
<httpHandlers>
<add verb="GET,HEAD" path="ScriptResource.axd"
type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions,
Version=1.0.61025.0, Culture=neutral,
PublicKeyToken=31bf3856ad364e35" validate="false"/>
</httpHandlers>

After this, I didnt get the error in the status bar. But the button click
does not work now. I found that the Button is not working since it is placed
inside the Updatepanel,

What is this Httphandler means? Why this is not firing the Button click
event inside the updatepanel?

When I copy the same project in another pc, the button click works fine even
when the httphandler is added to web.config file.
But its not working in my pc.

My main objective is to fix the error in the status bar.

Can anybody help me?

--
Regards
Valli