View the source file, browser-test.html, in IE7 and Opera 9.22.

In this file, white-space: pre; causes the text in <code> to display beyond the right side of <div.codeblock> in both browsers, though it looks fine in EW. Removing white-space: pre; eliminates the problem.

What was it suppose to be doing and why is it a problem, now?

White-space: pre means the page will display exactly in the same way as the source code. If the code runs together it will overflow out of the box while if the source code has new lines and spaces they will show as well.

Play with the source code formatting in the white-space: pre section.