OpenX, as a really great free and open source ad server, has capability to prevent the same banner showing up more than once on a page.

For this to achieve, you have a couple of options during generating invocation code for a zone:

- Don't show the banner again on the same page

- Don't show a banner from the same campaign again on the same page

These options are located below the main invocation tag. Select any of the options depending on your needs and click Refresh for generating new invocation tag.

After the invocation tag is generated put it on your site.