You should ask what annoys users.

Pop-ups/lightboxes.

Changing the default scrolling behavior.

Sites crippled with ads.

Slow sites.

Google analytics everywhere.

Unreadable text (light gray on white, what could go wrong?)

Unzoomable sites. You know not all people can see perfectly well. I need to zoom to be able to read.

Sites working only on $X browser.

Headers sticking to the top, consuming screen space.

Lots, of other stuff...