It seems like you have enabled debug redirection. This can be a very useful feature when debugging workflows, but it indeed can be very annoying when you don't need it.
But don't despair, you can turn it back off! In site.ini.append(.php) in settings/override/ and settings/siteaccess/<i>yoursiteaccessname</i>/. Just remove this line, or replace "enabled" with "disabled":
