I am building a website and I have swfs and scroll lists in it. When one views these, and then returns to them, they are still how they last viewed them, for example the swf gallery is not on the first photo but on the one the user last viewed. Scroll data is even left with the scroll thumb at the bottom (or where the user previously left it) not at its initial state...
Is this common with flash or just with flash catalyst?
This is common to Flash Catalyst, Flash Builder, and the Flex SDK. Pages and states remain in the same condition you left them.
For Flash Professional, I believe it depends largely on how you create the swf and list, though I am less familiar with that product.
For the swf in Catalyst, you can use "gotoAndStop" or "gotoAndPlay" to reset it.