Hello, I started web developing few days a go and I have basic understanding in HTML and some what for CSS.
I started because of interest and culturally I'm trying to design a website that is similar to this website ...
I know (I think) it uses JavaScrip to achieve the auto sizing... I have no idea how this person on Twitter built this website. Please help me construct this sort of website!
That site does use a bit of JS, but not to good effect, really. It looks incomplete; but anyhow, using JS in that way isn't a great idea, as the page is a bit broken with JS turned off, which goes against good practice.
Because this is a forum—rather than a web design service—it's best if you make a start at your site, show us what you've done, and ask advice on certain issues, rather than simply asking how the whole thing is done. If you have no idea, that's where it becomes better to hire someone.
You do have the option to look "under the hood" at the code used on that page. It's all there to look at—for example, by right clicking on the page in Chrome and choosing Inspect Element. It's a bit like learning to fix your own car by looking under the hood and studying the component parts.
I take it you are talking about the responsiveness of the site? is that what you are interested in? if so do a youtube search for "@media responsive design", look at twitter bootstrap and look at skelton.js .. I personally dont really think that site is "all that" in terms of design though, but responsive design is very very cool indeed.