if you want to apply and test out the yahoo ad network? I'm interested because google is paying like crap now
I don't think its necessary. In fact it shows that your site is already approved for adsense, if at all that matters to yahoo
You can't show AdSense ads and YPN ads on the same page. You are free to rotate the different ads on the same page or put different ads on different pages.
but when i apply for yahoo do i need to take down the adsense ads to get accepted or can i leave them up for now