The 42 floors website is JavaScript heavy, so if you want something comparable you'll want to be well versed in the three web languages; HTML, CSS, and JavaScript. Codecademy.com is a great place to get started, and there are plenty of free resources online to help you along. With focus and determination, you'll be building JavaScript apps like 42 floors in no time.
1. Learn HTML/HTML5 - I can't really recommend anything here. I just sort of picked it up.
2. Learn Ruby on Rails - http://ruby.railstutorial.org/. You can probably pick up a lot of HTML and CSS from this tutorial. I spent about 50 hours working through this. You're probably looking at 80 hours or so.
Once you've put about 200 hours into the the above, I'd say you're probably capable of building a working website. It won't be pretty, but it will work.
Got the picture.
Well, that will not put me down.
I have CS degree, I have 14 years experiences in High-Tech industry as a QA and lots of knowledge.
My goal is to be a founder of a similar site (technically) like 24floors.com and I need to start somewhere.
Thanks tzaman.
Truthfully it depends. Some people pick up on stuff quickly. Just come up with an idea and start building. I find that the best way to learn. If you get stuck just Google.