webconfig issue

Hi.

The problem is with this System.Net.Http.Formatting dll. When you add a new dll then it's reference will exists  in the web.config file. But in your case the install dll version in the bin and the reference of that dll in web.config file doesn't match. So if you check the version in both the point you can able to uderstand properly. Try to update the version or set the previous dll version as per web.config file. 

Thanks. 

try below links

1) https://stackoverflow.com/questions/22403650/could-not-load-file-or-assembly-system-net-http-formatting-or-one-of-its-depen

2) try