popup on command

I know in this day and age of popup blockers its getting harder to allow users to see these things. In my site however in order to get help on a form (i.e. if you do not know what to enter into the input area) you can click on a little [?] button beside the input area. I want to make a popup occur that displays help for that subject.

So if I were to just make a <a href="blah.html" onclick="document.open(whatever)"> would a popup blocker block that? Since the user is clicking on the link I would think not however I have been wrong many times before.

Some might some might not. The only way to tell is to try it.

I'd do it like this:

<a href="whatever" target="help">

That way you're not relying on the user having JavaScript enabled and it's less likely to trigger a popup blocker.