Upgrade to IE 9

Dear All Forum Members,

I want to upgrade my asp.net application which is designed for use with internet explorer 7.

But now, I want to upgrade it to internet explorer 9.

What changes i have to made in it?

Currently, i am using our IE7 compatible website in IE8, IE9 using following code.       

<httpProtocol>           

<customHeaders>               

<clear />               

<add name="X-UA-Compatible" value="IE=7" />           

</customHeaders>       

</httpProtocol>