🧵 Two of my most- and first-used checks when doing a performance audit are surprisingly old school: 1) Validate HTML 2) Disable JS.

Validate HTML? Yep. We haven’t really cared about ‘valid HTML’ for valid HTML’s sake for about a decade, but certain errors can actually be pretty significant. What’s wrong with this picture?

It’s this lil’ fella right here. isn’t allowed in the , so when the browser encounters the , it assumes the should have been closed already.

This is a feature. This is what allows us to omit certain closing tags like

, , , and—you guessed it!—. The appearance of certain opening tags implies the closing of certain preceding ones.

The practical upshot of which is that non- elements early-terminate the tags, pushing all of your important resources into the . Oops!