Step 1: Visual Studio 2010 >> Tools >> Options
The first step is to open visual studio 2010. Select "Tools" menu and select
"Options" item from it.
From the Options dialog box expand Debugging node from the left tree view and
then select Just-In-Time node listed under the Debugging node.
In the right pane check all the three options if they are unchecked.
Step 2: Change Config file
In the config file please ensure that the "compilation" tag should have "debug"
attribute set to "true". As shown below.
Step 3: Set default browser to IE
In visual studio, Right click the .aspx page and then set IE as default browser.
Step 4: Place the breakpoint in javascript and press F5
Now it's the time to place breakpoint in javascript and then press F5 (visual
studio should be attached to the page).