basic game movement

How could you say make a x move around a grid using the arrow keys?

I think you might do better reading a tutorial for this question.
Here's one that you might like, but you can find others on Google:
http://www.brighthub.com/hubfolio/matthew-casperson/blog/archive/2009/06/29/game-development-with-javascript-and-the-canvas-element.aspx

Basically, moving "thing" with the arrow keys involves:
1. making an "x" and "y" variable (to store the object's position)
2. capturing a keyboard event to change the "x" and "y"
3. clearing the screen and redrawing "thing" to the changed "x" and "y"

I won't explain it in any more detail (though someone else here may), because so many other people have done a good job of explaining exactly what you're looking for.

thanks