I'm seeing some slow loading too, even by my connection's standards (which ain't that good, so if I'm seing slowness, it's slow). Even a View->Source is slow (it re-fetches the HTML, so that means that the problem isn't the images, JS or CSS).
The only way to fix the alignment is to let go of the idea that the boxes should be part of the background. (My current screen is 1920 pixels wide, and I get empty boxes on the right-hand side of the screen when the background-image repeats, as well as text that appears to be afraid of the containers you intended for it.) You can't assume IE on Windows anymore -- that was a 90%+ chance a few years ago, but it's down to a coin toss these days.
What you have at the bottom is a genuine, honest-to-goodness table of data. It should be in a table. (I know, I know -- you keep seeing things on the web and in books that tell you never to use a table for layout, and they're all right. In this case, though, you actually have a legitimate use for, and I'd say need of, a table.) Creating something very similar to your box graphics in CSS alone would be easy; making it work in IE (which doesn't yet offer rounded borders) as well means using two small images in addition to CSS (one image for the top of the box and one for the bottom). You would then simply set the background colour of some cells to blue, some to white, and others to transparent and presto change-o, you've duplicated what you were after with no alignment problems.
(If you need help with that, post back, but in the Graphics and Design section. We're a pretty good community around here.)