Sometimes I notice that ad units are not loaded and its just blank (white) instead of showing any ads at all (including PSA's) This seems to happen more frequently when I run only image ads. Is it because there are no relevant ads to display? And if so, is there any way I can make it show a text ad instead when this happens? There is a part of my site where I prefere image ads to be displayed, but its kinda crappy when 50% of the time nothing at all is shown..
It happens to me too. I use both text as well as image ads. Sometimes (rare) it will show nothing. I think the problem is with Google.