Completely Stumped

Hi Guys, can someone please tell me why this doesn't work in FF:

HTML:
<img omousedown="foo(this)" src=.....>

JS:
function foo (item)
{
item.style.position='absolute';
item.style.top=200;
item.style.left=200;
}

This works ok in IE, but in FF I get: Error in parsing value for property 'top'.

I've tried setting top and left in css, so that FF has an attribute to work with - but this has no effect.

This thing is driving me mad, if anybody has any ideas, I'd be very grateful.

Thanks.

Solved. FF requires 'px' appended to the value.

Thank you me.