2024-10-30
Keeping your site accessible to old browsers is non-trivial
One of the questions you could ask about whether or not to block HTTP/1.0 requests is what this does to old browsers and your site's accessibility to (or from) them (see eg the lobste.rs comments on my entry). The reason one might care about this is that old systems can usually only use old browsers, so to keep it possible to still use old systems you want to accommodate old browsers. Unfortunately the news there is not really great, and taking old browsers and old systems seriously has a lot of additional effects.
The first issue is that old systems generally can't handle modern TLS and don't recognize modern certificate authorities, like Let's Encrypt. This situation is only going to get worse over time, as websites increasingly require TLS 1.2 or better (and then in the future, TLS 1.3 or better). If you seriously care about keeping your site accessible to old browsers, you need to have a fully functional HTTP version. Increasingly, it seems that modern browsers won't like this, but so far they're willing to put up with it. I don't know if there's any good way to steer modern visitors to your HTTPS version instead of your HTTP version.
(This is one area where modern browsers preemptively trying HTTPS may help you.)
Next, old browsers obviously only support old versions of CSS, if they have very much CSS support at all (very old browsers probably won't). This can present a real conflict; you can have an increasingly basic site design that sticks within the bounds of what will render well on old browsers, or you can have one that looks good to what's probably the vast majority of your visitors and may or may not degrade gracefully on old browsers. Your CSS, if any, will probably also be harder to write, and it may be hard to test how well it actually works on old browsers. Some modern accessibility features, such as adjusting to screen sizes, may be (much) harder to get. If you want a multi-column layout or a sidebar, you're going to be back in the era of table based layouts (which this blog has never left, mostly because I'm lazy). And old browsers also mean old fonts, although with fonts it may be easier to degrade gracefully down to whatever default fonts the browser has.
(If you use images, there's the issue of image sizes and image formats. Old browsers are generally used on low resolution screens and aren't going to be the fastest or the best at scaling images down, if you can get them to do it as well. And you need to stick to image formats that they support.)
It's probably not impossible to do all of this, and you can test some of it by seeing how your site looks in text mode browsers like Lynx (which only really supports HTTP/1.0, as it turns out). But's certainly constraining; you have to really care, and it will cut you off from some things that are important and useful.
PS: I'm assuming that if you intend to be as fully usable as possible by old browsers, you're not even going to try to have JavaScript on your site.