Centering a box

Hi - this is the dumbest problem, I can’t get a box to center-align. I’ve tried both:
margin:20px auto 0;

both individually and together and it won’t listen to me! Please can anyone see the error?

I’m trying to center the top subscribe box with its header, applying the rules to .mastheadsub

Adding margin:auto; to the rules for .awboxtop works for me, if I’ve understood what you’re asking.


Thanks for your quick response! I was avoiding any change to that class because it’s also used as half a table cell when I add image to header, see:

But as you say, it works! And all it did when there’s an image too, is move the subscribe box over to the right, closer to the image, which is fine with me. Thank you!