I saw some people showing adsense ads on wait loading before showing their content. Anyway it's just in a small block in the page. is this allowed?
I suppose if the page is with NO content, then they are certainly broke Adsense TOS. But if the page have some content, page load is quite long (to give time for people to read) I think that is acceptable.
let say it's a video sharing site, all contents are showing except the video area that show ads before video show up.