about Javascript

I found Javascript is very interesting. At the beginning, it's not easy to understand. But later I try to write a new function. It's not so difficult and it's a bit like Actionscripts. I think this one is the only programming language which I can use before this semester although not very well.
The following is just a reminder to myself.
The script part is in head tag and is used to define a function with the code like
function rollover(imageName)'document.getElementByld(imageName).src='image01.jpg'';

Then in the body use this code,
in the 'a' tag
onmouseover="rollover('pic1');"

followed by the attributes of the image, the respond area.


the name of the function can be anything. and if hire more than one function in the body part - just follow the first one(without any symbol)

pic1 is the imageName, the id.