This is answered in the article (pretty far down, I'll admit): >But if all we have is the link, there are two problems here that we haven’t addressed. >The fi

This is answered in the article (pretty far down, I'll admit): >But if all we have is the link, there are two problems here that we haven’t addressed. >The first one is… you go visit this site and it delivers some code to you. How does it know what kind of code it should deliver to you? Because if you’re running on a Mac, then you need different machine code than you do on Windows. That’s why you have different versions of programs for different operating systems. >Then should a web site have a different version of the code for every possible device? No. >Instead, the site has one version of the code—the source code. This is what’s delivered to the user. Then it gets translated to machine code on the user’s device.