I did a search to no avail...

... on my development site, I am putting an HTML block with a greeting, followed by recent comments and recent topics. It seems the blocks are going to the extreme far right of my browser and are even going past the margin when I am not at full screen (1280 x 1024). Is there a setting or somewhere in the template that will let me reduce the width of the table or div that is "going all the way"?

I also noticed that - if I put blocks on the right, then they are "underwritten" (maybe z-order?) by the center blocks.

If you've put in fixed width or something like that in the templates, then that could be the case. I suspect that the problem originates from your theme. But I can't be sure without seeing it. Check width's (either fixed or %) there might just be something a problem there. Might also be a colspan or row-span related problem.

Thanks.

BTW, I'm using the default template. I actually kind of think it is the best for my given site.

No problem. If you use the default template. Then I'm sure it's a problem in your theme, so no need to check the templates