mac os x - not getting headers already sent error

I do all my development on mac os x. sometimes, to debut a script, i output the query to the page. quite often the page sends headers to go to another page. When i do this, i comment out the header() function and read the results. When i'm done i remove the comment Sometimes I've forgotten to take out the debugging output. Now, on my server here, the page redirects and loads fine. But in the live environment, it craps out and people are left staring at a blank page. The test server is the same computer i'm developing on. Anyone know why this happens, and how i can fix it? Jon Haddad