For some reason, adsense ads won't show up sometimes. For example, all ads might show up on a page, whereas on somepages no ads will show up, and in some only a few will show up. There will usually be a blank screen but when you highlight that area, you can clearly see the banner outline. What could be the problem?

http://www.aandhi.com/videos.htm
As you can see, the leaderboard at the top shows, but not the banner on the bottom (below the line break)

can someone quickly tell me what could be the problem? Because on some pages, the same banner will show up in a similar position.

under the orange line break?

i can see a 468x60 google ad in firefox

google doesnt have enough relevant ads to serve those pages.

Google AdSense is not always able to find an advertisement which matches the content of your web page. Normally, AdSense selects a Public Service Ad (PSA) and displays it in your ad space. These PSA's generate no revenue for you.

Google has created the ability to load an alternate ad when it cannot find a matching ad. This is accomplished by setting a variable called google_alternate_ad_url in your AdSense layout code:

google_alternate_ad_url = "/adsense-alternate-ad.shtml";
These alternate ads can include advertisements from Google AdSense competitors, such as Clicksor.

This capability enables you to tap into a revenue stream which would normally by lost to AdSense PSAs.

But the Google Terms of Service disallows you to use any other service similar to Adsense? How can they allow Clicksor?

I have no clue. I personally don't but I see a lot of other people do. You may also find this article as a good read. It actually explains how you can show your own ads for your own sites in the place of those psa's or blank spaces.

http://www.sitepronews.com/archives/2005/aug/19.html

I got a problem with ads as well mainly image ads.
now the thing is its working fine on my local machine but when i go live one of the ads don't work?

any help?

thank you

seems fine to me, sometimes the page load is very slow, could be your server slowing down sometimes