Rounded image/table corners

[jordannamorgan]

This is probably a question I should have asked a long time ago, but it's come up again in my updating of some old layouts, so. :Þ

A couple of different layouts I use (including my own journal and prose_alchemist) not only give rounded corners to entries and modules, they insist on rounding off the corners--or sometimes half the corners--of my header images as well.

Is there a way I can get rid of all the rounded corners, and just have nice, straight, angular ones? I'd like to do that with the header images and entries/modules, although I'd settle for just not having the corners of my headers forcibly rounded off. (If I wanted them rounded, I would have made them that way, DW...)

EDIT: issue solved! CSS to do the trick is here in the comments. Thanks for the helps!