'Episerver.UI.WebControls.ControlAdapters.HTMLHeadAdapter' is located in the file EPiServer.UI.dll. So if you get this error check the bin folder and the GAC for that file. Also make sure that it's the correct version, in this case 5.1.422.256.
EPiServer CMS development team.
I installed Episerver CMS 5.1.422.267 and later uninstalled .After that i installed Episerver CMS 5.1.422.256.When i run an application which is devoleped in Episerevr CMS 5.1.422.256 in that machine i am getting an error message
Could not load type 'Episerver.UI.WebControls.ControlAdapters.HTMLHeadAdapter'
What is the reason for this error