[masklinn]

> You usually won't know a web page is actually using H5BP, especially without looking at the source.

One of the ways to know, before the new release which sadly kills it, was that many sites didn't customize the default hot pink text-selection background color.

Select text and get hot pink? You knew it was the boilerplate.

[pav3l]

Also I imagine many wouldn't customize 404 too much

[masklinn]

The 404 you usually had to hook in yourself depending on your server & framework, so that was way less likely.