After installing Umbraco, it is likely you might see this error message when you try to load your website:

When you look in your web.config, you'll notice you can't find the host entry.  Instead, have a look within the web.config in the Views folder. In here you should be able to find the MvcWebRazorHostFactory entry to remove it. One thing to note.. at the end of the line is a closing tag.  Do not delete this otherwise you will see a missing tag error instead!