Literal content ('       ') is not allowed

Hi, I'm having a problem that when I switch from design to source then try to run my webpage, I get the following error:Literal content ('       ') is not allowed within a 'System.Web.UI.WebControls.DataControlFieldCollection' So, I had to clean my webpage from ('       ') characters to fix it, then it happen again ... and I had to go through this process many times to fix my webpages.So, where space characters are coming from (&nbsp) because I haven't included them!!!?Go to the complete details ...