IIS: There was an error while performing this operation
This is more of a tip than a post. Today I had the following error in IIS while modifying Handler Mappings
There was an error while performing this operation.
Error: Cannot write configuration file due to insufficient permissions
We are using TFS, and TFS sets the Readonly flag when the file is checkin. Basically, all you need is to check out the web.config before do your modifications in IIS