[herpderperator]

Don't forget progressive JPGs, which loads the entire height of the image over and over with gradually increasing detail.

[kalleboo]

There was also LOWSRC, which is long gone nowadays https://html.com/attributes/img-lowsrc/ https://bugzilla.mozilla.org/show_bug.cgi?id=92453

[zpr]

Shhhh... Or my boss will hear you