hi Y.,
from what I've read temper tantrums are really quite normal. (As you may have noticed, even adults have them--but that's probably a sign that they weren't given the tools to deal with their emotions when little). My son was having this problem some time ago, and at first I just got angry at him and we butted heads--that made the situation worse.
Then I read a really interesting article on mothering.com (excellent parenting site which advocates 'mild discipline'). I recommend you go there and read what they have (I just googled 'tantrum'.) Then I tried the following approach: I would let the tantrum happen without trying to stop it, while keeping calm (that can be hard sometimes, I know) and eventually I would ask "do you need a hug?. The answer was invariably yes. The tantrums have gotten much better, but he's now (at age 3 and a bit) able to ask for the hug himself as soon as the tantrum starts, and that immediately makes it better.
The theoretical basis of this is that young children simply have a very hard time controlling or even understanding their emotions; anger for them is like an uncontrollable force that takes them over. It can even make them scared of themselves, not to mention make them scared that you will not love them anymore. So what they need is reassurance that you are there to help them through this, that you love them through it. Later on when they are calm and the storm has passed, the parent and child can talk about what is appropriate behavior and not, why the child got angry, that it's the anger itself is ok, though it's not ok to take it out on other people by for example hitting or insulting them. Eventually, if all goes well, the child will learn to deal with the emotion successfully.
Good luck!
G.