What forum for help about building banner ads?

The title says it all. I’m not sure if this is the right forum for discussion of banner ad creation techniques. If not, can point me in the direction of the correct forum, be it on or off this site?

Alternatively, here’s what I need to know. We have a large 975x300 banner we want to display for five seconds, then have a 975x35 banner ad appear in the same space. Any ideas on how to do this in Google DFP?

Google DFP suggests step by step process about your problem. You should use Google DFP forum: https://productforums.google.com/forum/#!forum/dfp regarding this.