[eluser]tonanbarbarian[/eluser]
99 times out of 100 it is a blank line AFTER the closing ?> tag at the end of the file.
I have posted about this before (too lazy to try to create a link to it) but to summarize what I said... just do not use the closing ?> tag in the file if there is nothing coming after it. It will marginally speed up your code and will mean you never get the above issue.
If you are interested in some more explanation as to why and also some other tips on coding standards just search through my posts, there are a couple of posts about it from late last year
