Is it just my iPad that does this? How do I stop it?

[Gettheetoanunnery]

Bear with me while I attempt to explain this...
Say when I go on a website, then click on something that brings up another smaller screen in the foreground with a drop down menu, I can't scroll through the drop down menu as it just scrolls the background page instead. Do you know what I mean?

It's annoying cos if I go to buy something online and an extra menu comes up to add card details for example then I can't. Is there a way I can get past this?

I get this on some but not all websites. So I think its that some websites are more ipad friendly and some aren't. There's certainly times when I've had to fire up the laptop to fill out a form, etc. Not very helpful, sorry.