In FireFox 2.x, the last blog post n "Recent Blog Posts" prints over the bottom of the box.
In Opera, long post titles overwrite parts of your AdSense block, which can get you into trouble with Google.
You should probably delete the "Hello World" post.
You should update the "About the Blog" section.
You should update the "About" page also.
In addition, you should delete the default links which are still in the blogroll.
120x600 skyscrapers have never been a good performer for me. You might try other in-content ad blocks. The rectangles usually work best for me.
Some of your post titles capitalize important words, other don't. Pick a standard and stick with it.
Best of luck on your new project!