I noticed that there are times when making a post where I try to post the source at the bottom of the article the scroll bar drops before I get a chance to post the source.

What causes that to happen?

I've noticed it on long posts which is understanable but it also happens on average length posts.

Is that something unique to phpBB formats?

It's happening to me as well. It is not easily explained. When you type your commentary, then post an article, when you then go to add the source(or fix a typo), the page keeps going back to the top where you started to type your commentary. I have seen this happen on other forums, but only by times. It seems to be happening with every post. I thought it was just me, until T brought it to my attention that it was happening to him as well.

Here is an example of what I mean. See where I had to put the source because the scroll bar kept dropping .

http://www.americanpoliticsforum.com/topic73.html

NP. I can get around it by posting the link at the top instead of the bottom to avoid the problem.