I’ve used this site every time I’m doing http networking stuff for the past few years. It’s so easy to just go to http.cat/303 to check a status code you don’t know, or to scroll down the homepage to find the number you need for a specific response.

The cats make it much more fun than a regular docs page, whilst still being a useful quick reference. I wonder if other bits of reference information could be made more interesting in this way.