problem testing a website on iis

Problem testing website on iis
hi i created a simple website on asp.net and i tested it and it works fine on visual studio but when i try to test it on iis it does not work it returns an error
I'm testing it on my laptop and i have the iis that is installed in window 7


Server Error in '/cse' Application.
Configuration Error
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: Unrecognized attribute 'targetFramework'. Note that attribute names are case-sensitive.

Source Error:

Line 15: </connectionStrings>
Line 16: <system.web>
Line 17: <compilation debug="true" strict="false" explicit="true" targetFramework="4.0" />
Line 18:
Line 19: <authentication mode="Forms">


Source File: C:\Users\jb\try\web.config Line: 17

looks like the problem is that my web config is set to net 4 and the iis application pool is set to 2 so i tried to change the application pool to 4 but it didn't help and it seems the page is still running on because on the bottom of the error it says

Version Information: Microsoft .NET Framework Version:2.0.50727.5420; ASP.NET Version:2.0.50727.5420

so maybe there is a different way to change the net

i also tried to change the config file to net 2 but it also failed to work

any ideas help?