they have approved my ads and on the ads i always see Advertise on this site Powered By AdBrite when another of my friends site who has same alexa ranking got different ads all the time
Everytime you won't see ads...there are target ads to certain geographical regions..... Maybe you have just added adbrite...wait for sometime until more ads are approved
it depends on geo-targetting as well ... to cover that "Advertise on this site" set your pricing options in your zone to show other ads, like bidvertiser you'll never leave that space blank that way
I would have an email with Adbrite about this. It happened to me once and I had to contact adbrite and it was fixed.
I have been experience this earlier. It is either your page keyword is not enough for them to know what advertisement to put and run there. If you think the content is good enough, they might have issue with your account. I have these problem earlier and they have get my account fixed.