CSS Questions

Hello,

Is it possible to edit the CSS to allow a block to appear above the left and right sidebars? What I'm looking to do is something similar to the Salamander theme (http://drupal.org/project/ability - it's the blue area below primary links). The point of doing this would be to add a welcome message via a block that would appear on the front page. I know how I could do that, but I'm unsure as to how to edit the CSS so that the block would appear in that manner.

Thanks for all of your help!