Help please

I wonder if you can help me please.
I have just uploaded my new site and after running a W3C validation  
it came up with 143 errors. Your 'TidyUp' thingy seem to give me code  
to replace but when it did it threw the whole page out, missing links  
and backgrounds etc.
Even when I went in to the individual lines and looked for the  
trouble I couldn't find it. I have searched the forums and I can't  
find any documentation anywhere. Maybe I am just not getting it. I  
would appreciate your comeback though.
My site is www.pixarcreative.com, I built it in Joomla 1.5 using the  
'RT Novus' Template.
Kind regards
keith

Pixar Creative - creating imagery that works!
Tel: 0141 616 3322 Fax: 0844 209 7422
See our new website at:-
www.pixarcreative.com
info@pixarcreative.com
www.gogreener.org.uk