Help, please?

~No matter how I resize the picture, I cannot get it to expand across the header box. Putting in a much bigger picture--no matter what its proportions--results in a taller image (and header box) but nothing I've done makes the picture any wider than it is now. Blogger help's suggestions don't work either. Any ideas?

~Is there a heuristic for sizing photos? I've figured out some of the code just by changing things to see what happens, but I can't figure this out.

~ETA--failing to increase the size of the picture, I simply made the box smaller. But it's not an ideal solution...

~ETA2--several hours later, the picture has shrunk. I kid you not. It used to fill up the box, and from where I'm sitting it no longer does. And I've done nothing to it. I just don't get it.

~ETA3--I give up. This picture's not supposed to fill up the whole box....

Testing things out

Just trying things out....


ETA: I am SO frustrated. I had a picture fitting almost perfectly in the header, and I messed it up, and now I can't make it fit no matter what. ARGHHH