Blog Question For Anyone that can answer the question

Dear Friends

I have a question for anybody that can answer this question which has to do with Blogger...

Why is it that when I go to customize my Blog - like make different sections of it different colors, or different widths and so forth that there is always a Error Code that shows up and than it won't let me do anything. 

Is there something that I can do to get rid of that Error Code?  I found a real pretty background template that I would love to use but I can't change the widths or anything like that...I keep getting the stupid Error Code.

Thanks In Advance
God Bless You
Love & Prayers
Linda K, Railroad