Does anyone know how to counter/prevent this? I always get hit by a focus when I'm getting up after being knocked down. Then I get ultra'd. And lose a lot of health. And it hurts.

Like, when i get knocked down, the opponent starts charging his focus. Then right when I"m up, he focus attacks me and I fall again. I do this to other people too sometimes, but I was wondering if anyone knew how to prevent it.

Try to grab them. I'm not really sure if it would work but if they are close enough for a focus attack they are probably close enough for you to grab them.

I sometimes use this tactic but it can be pretty easilly countered, you just get up straight into a special move, for example I use Ken's shoryuken or Cammy's cannon drill, they break focus attacks no problem. I also consider going straight into my ultra if it's charged. Don't think of it as the opponent getting you pinned, think of it more in terms of the fact that they just left themselves wide open. 

Yeah I'll try those, I guess you have more time than you think when you're getting up
thanks

Also when you fall pressing down right before you hit the ground makes you come back up much quicker giving you more time to counter or even preventing them from starting the focus at all.

I think every character has a move they can do from the ground that has a certain amount of invulnerability at the start, if you time it right you can start the motion for the move right as you're getting up and the instant you're on your feet you'll do the move, it should either break their armor, or counter the focus attack if they've already let it go

low heavy should work, but if the person times the focus attack perfectly its gonna be tough to counter especially if you are a new player and can not pull off moves under pressure.

yeah the focus is only unblockable if they charge it all the way. if you tap down just as you hit the ground u will get up more quickly buying time. from there id block or throw or something.

"I sometimes use this tactic but it can be pretty easilly countered, you just get up straight into a special move, for example I use Ken's shoryuken or Cammy's cannon drill, they break focus attacks no problem "

Also any of the attacks on a character's movelist with a red star next to it can break their focus attack and hurt them.  Sagat's Knee Crush for example.