I recently made some changes to my Optica themed blog on Tumblr; specifically, I changed the height of the header image in the custom css section. Problem is, now I have this huge space between the header and the menu which I can't get rid of. I tried removing parts from the source, but to no avail.
You can see the blog here: http://ilconfess.tumblr.com
You have your height set to 350px in your css.
Check main.css line 539 and set height to Auto.