[r3n3gad3]

Originally Posted by Simon

Yes, the doctype declaration is important. If you're not going to follow the strict rules, you can always use HTML 4.01 Transitional instead of HTML 4.01 Strict, and you can use XHTML 1.0 Transitional instead of XHTML 1.0 Strict.

[...]

Some reading on doctypes:
http://www.alistapart.com/articles/doctype/
http://htmlhelp.com/tools/validator/doctype.html
http://www.w3schools.com/tags/tag_doctype.asp
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Now this is the reply I needed, thank you Simon