500 - Internal server error.

hi i published my application and uploaded the documents to the web host, however i keep getting this error when i try to get to it on the net "500 - Internal server error." How do i debug it to find out what is causing it. I have also attached my webconfig incase anyone can see whats wrong with it;
<?xml version="1.0"?><configuration> <configSections> <section name="rewriter" requirePermission="false" type="Intelligencia.UrlRewriter.Configuration.RewriterConfigurationSectionHandler, Intelligencia.UrlRewriter"/> <sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"> <sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extension ...