This applies mostly to mobile sites but it's sometimes an issue on desktop sites too.

I HATE it when I try to tap a link as the page is loading, but just before I tap it some element or other of the page loads and makes the page jump suddenly, making me miss the link and hit something else.

You'd think web designers would have fixed this issue by now. Or is it impossible? I can't see why the browser couldn't work out the size of all page elements first and create placeholder boxes which would retain their size as each element was loaded. Would this be possible somehow?

Patience link hopper.

It's easy to fix - but it would mean the web designers would have to get rid of all the useless, unnecessary crap they insist on adding to every page that prevents things from loading quickly.

I almost believe it's intentional. Drive up ad click revenues.

One of my pet peeves - on web sites like CBS, commercial breaks that take over the player making the playback and volume control unavailable. The only way to pause playback or hit mute is to click on the screen - which of course generates a click because it leads you directly to the advertising company's web site.
 
I don't know if those companies realize that annoying tactics such as these mean that I (and others I assume) will systematically boycott them  - I'm talking to you Khol, Target, Microsoft...

I think auto-playing videos on news sites is my second peeve. There is nothing worse than visiting a page and before you have time to react, some loud ass local news jingle starts blasting through your speakers. Any kind of auto-playing audio is extremely bad web etiquette. I thought most web designers had learned that by the year 2000 but obviously not...

I'm right there with you!  it bugs the begeebers out of me to tap or click on something before the page finishes jumping back and forth.  sometimes the page even disappears near the end of loading everything just to reappear with everything loaded.  that bugs me too.
 
and the autoplay is AWFUL!  I've even run across some sites which didn't even have a way to turn it OFF!!!

Some browsers can be configured to only load plugins on demand.

Beagle
and the autoplay is AWFUL!  I've even run across some sites which didn't even have a way to turn it OFF!!!

NagBap plug-in? 

Given that are umty-eleben ways (i.e. languages/tech ctacks) to build web sites, no standards have yet to be agreed upon (nor proposed) since every tech stack thinks THEY have the answer.
 
Unlike the DAW world, eh?
 
Just export/import a .wav, .omf, .mp3, .dot.dot.dot sumpin
 
Just make sure it's the right bit and sample rate else your friends DAW will puke.