Layout isn't bad at all, there's only three real things I can pick at from a designer standpoint.
1. the contrast between the red "regex' and the background is way too low. Consider lightening/darkening either that bit of the title or the background to make it pop a bit better from the background. Low contrast text can make viewers uncomfortable, even if it's the title
2. at the bottom of each page you have alternate links (same as the ones in the main navigation) is a Next up:, Please... Make it bigger.. make it bold. I didn't even know it was there until I really started searching. It's nice to have those at the bottom but make more of an effort to make them stand out then just making the link blue. This gives your user more of a visual cue that "yes.. there actually is something different than just body text down here!"
3. I clicked on site home under the little pixel portait.. and I got lost. The only way I could find my way back to the regex part of the site was by hitting the back button or searching under the computing header. The moral of the story is that programmers have short attention spans, we won't work very hard to find information. If we go to a site for help on something, like regex, and we somehow get lost on that site... we leave.. fast. A lot of people haven't got the patience or time to try and figure out what the heck is going on. You've got some really great info on your site, just don't let your users get lost!
I've worked with Regex quite extensively, I love using them because they make things so nice and simple in my php. I can't really tell you if it's good for a beginner or not (regex aren't exactly for beginners anyhow)