Unrecognized attribute 'targetFramework'. Note that attribute names are case-sensitive
This Error occurs because of following reasons.
1. On your Server, .Net Framework 4.0 is not installed.
2. If installed, then Framework 4.0 is not selected
on the Application Pool of your Website.
First of all check whether .Net Framework 4.0 is installed on your Server.
For checking that, open your IIS and go to your Website.
Right Click on your Website --> Select Manage Website --> Select Advanced Settings.
Note down the Application Pool of your website from Advanced Settings.
From Application Pools List above Sites node on IIS, select your Application Pool.
Right Click on your Application Pool --> Select Basic Settings.
A new window will come as shown in the figure.
Check whether on Dropdownlist named .Net Framework Version , 4.0 is listed or not.
If listed, then select .Net Framework as 4.0.
By this way we can resolve this issue.