I was reading about server optimization here:
http://developer.yahoo.com/performance/rules.html and it mention the use of php_flush just after the </head> to get the ball rolling and at least get all external css loading (it's implied that the css files download load right way, I guess).
I was curious if anyone had tried it and if it conflicted with vBulletin in any way. I'm always a little cautious with this sort of thing with vBulletin.
Brandon