This is certainly unmaintainable. There are two aspects I find especially interesting.<p>The first is how many different ways sites are determining the browser corresponding to the user agent. You know that they're all based on "guess and test": come up with an idea for an if condition, open up the code in the 5 browsers you care about, see if the result works. It almost reminds me of the output from a fuzzer: it's a valid answer, but you can tell a random number generator and a lot of tries is what got you there.<p>The second is how many web developers seem fine writing the same website many times; once for mobile, once for IE, once for Chrome, once for Firefox. I've always taken the approach of doing exactly one site, and using whatever features are available in the worst browser the client wants supported. If extensive workarounds are needed to make the feature work in every browser, I say skip it. (I was always happy with what IE6 could do.) Of course, when I did web development, it was mostly boring corporate applications, not public websites that face pressure from competitors that are willing to write a codebase from scratch for every browser back to NSCA Mosaic. I consider myself very lucky.