The white line is sorta bothering me. Maybe get rid of it? If you must have it, I would get rid of the part that goes down and just leave the horizontal part of it. Either have it solid or fade out.
Also double check to be sure your text is lining up. They seem a bit off.
Respectfully disagree. Nothing is wrong with white/negative space. It can be used used as a design element.
For text size, leave the blue font alone, but increase the white text by one point or so. It does look a tad bit small. Not a problem for me, but if someone with less than perfect vision tries to read it, then might have some difficulty. Are the two white fonts two different whites? The bottom one looks a tad darker...at least on my screen.
Oh and this is personal preference, but I never put "www" at the beginning of a web address. Unnecessary IMO. But that's me and doesn't affect the layout/design.