newbie help

[moepar]

Hi. I've just learned html & a little of css. I am currently reading up on the 'learn css' on the w3school (so I'm trying to figure this out). I was having a hard time with one of the examples on the site on a background image. The example from the site is at http://www.w3schools.com/css/tryit.asp?fil...ground-positionI'm using firefox (version 1.5.0.4), & when this displays as written in the example the smiley face is centered at the top with only the bottom 1/2 of face appearing at the top of the box. On my computer, it appears correctly centered on IE6, as it also does on netscape 8.1.I'm just curious why this happens this way? I know that some code just doesn't 'play well' with some browsers. Absolutely every other example appears as it should in the three browsers I have. Makes me feel like I'm losing my last 1/4 piece of my marbles!