So I came across this website (http://www.yourhtmlsource.com/myfirstsite/basicformatting.html) and I noticed that when you zoom in on the page, the text and the blocks that the text is in stay scaled so that the text does not flow onto more lines. I tried looking at the source coding but I couldn't find anything because the website uses an imported style sheet. I was wondering if anyone knew how that is done (what is kept proportional in the style sheet) so I could do the same for the simple web page I am making. Thanks.

Why not look at the imported style sheet then? Just follow the URL.

Anyway, the site seems to use a traditional fixed-width layout, so if you zoom in too much you get annoying horizontal scrolling.

That's what I would call not scalable. Different strokes...