Tips to resolve SharePoint 2013 upgrade issues "Could not load file or assembly 'Microsoft.SharePoint, Version=1.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c' or one of its dependencies."

After we migrated SharePoint from 2010 to 2013, we found several sites could not be displayed with the following error.

Sorry, something went wrong

Could not load file or assembly 'Microsoft.SharePoint, Version=1.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c' or one of its dependencies. The system cannot find the file specified.

After looking the welcome page URL for the site users try to hit. It’s something like http://servername.domain/site/default.aspx. However, this site is Wiki sites and the welcome page should be like http://servername.domain/site/SitePages/Home.aspx.

The workaround is to activate the “Wiki Page Home Page” web feature and the welcome page will default to http://servername.domain/site/SitePages/Home.aspx.

Please note if your site is not wiki site and you activate the “Wiki Page Home Page” web feature, users my "lost" customizations on the home page. You could always deactivate the same feature to display the customized home page that is defined as welcome page for the site.

Also this is very obvious but we had so many users complain about the site home page and this might be handy to resolve the issue for end users.