z-index property of css applies only for a positioned element. how if we define a style class for a position element, the position value is taken as relative and top & left values as 0 then what is the affect of using margin values of the element? How is it going to behave in different browsers? which is given more priority, margin or top and left for a position image?
Make a test page and take a
Make a test page and take a look. Far better than any response you'll get here. If you can't figure out why something should happen the way it does or why a particular browser behaves differently (or you want to make it behave the same as others) come back and ask a question.
Throwing up a test web page is a matter of seconds and you'll learn more.