simple beginners css problem

i have been on this forum for a while and i see that every body is always on about css. i have never done any thing with css being a action Script-er, never had the need. but i was making a little site of my own with css and have come in to a little problem:

[url]http://www.analogintelligence.co.uk/new/pages/showimage.php?image=82[/url]

the image is ment to be in the middle of the page but for some reason it s not in all browsers (except safari)? don’t under stand why because i have had no problems placing the “< last image” & “back to montage” & “next image >” buttons as these are placed with css so why dose my big image not place it self right?

this is part of my style sheet big_image is the the style that is not working:

#big_image {
position:absolute;
top:0px;
left:162px;
width:445px;
height:290px;
background-color: #333333;
overflow: hidden;
}

#box_b {
position:absolute;
top:305px;
left:162px;
width:100px;
height:30px;
background-color: #333333;
overflow: hidden;
}

#boxmid {
position:absolute;
top:305px;
left:334px;
width:100px;
height:30px;
background-color: #333333;
overflow: hidden;
}

#box_n {
position:absolute;
top:305px;
left:507px;
width:100px;
height:30px;
background-color: #333333;
overflow: hidden;
}

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