Seems like you got the code from svn but somehow didn't get the updated Web.config which has the needed control declaration or else overwrote it with your previous customized Web.config.
Back up your Web.config then right click it and do Tortosie SVN > revert then re-customize it with your settings.
For issues like this its best to put your custom appSettings things like connection strings in a user.config file which won't be touched when you do svn update. Though some other settings like smtp do require editing web.config
Hope it helps,
Joe