Please resize the viewpoint until the overflow box is 400px in width, which is the size of this block. Each background square is 25px in width.
Containing block = 200px.
Descendant block = ('margin-left' 50px + 'width' 100px + 'margin-right' 50px)200px.
Containing block = 200px.
Descendant block = ('margin-left' 50px + 'width' 100px + 'margin-right' 50px)200px.
Gecko 1.8: Containing block = 300px.
Gecko 1.8: Descendant block = ('margin-left' 75px + 'width' 150px + 'margin-right' 75px)300px.
Opera 9.5: Each overflow box with padding has extra space added on the right.
Containing block = 200px.
Descendant block (margin box) = ('margin-left' 50px + 'width' 300px + 'margin-right' 50px~0px)350px.
Containing block = 200px.
Descendant block = ('margin-left' 50px + 'width' 300px + 'margin-right' 50px)400px.
Gecko 1.8: Containing block = 300px.
Gecko 1.8: Descendant block = ('margin-left' 75px + 'width' 450px + 'margin-right' 75px~0px)525px.
Opera 9.5: Each overflow box with padding has extra space added on the right.
Gecko 1.9 & Safari 3: Scrollable box 'width' 450px = 'padding-left' 100px + ('margin-left' 50px + 'width' 300px + 'margin-right' 50px~0px) + 'padding-right' 100px~0px.
IE7: Scrollable box 'width' 600px = 'padding-left' 100px + ('margin-left' 50px + 'width' 300px + 'margin-right' 50px) + 'padding-right' 100px.
Containing block = 200px.
Descendant block = ('margin-left' 50px + 'border-left' 25px + 'width' 300px + 'border-right' 25px + 'margin-right' 50px)450px.
Gecko 1.8: Containing block = 300px.
Gecko 1.8: Descendant block = ('margin-left' 75px + 'width' 450px + 'margin-right' 75px~0px)525px.
Opera 9.5: Each overflow box with padding has extra space added on the right.
Gecko 1.9 & Safari 3: Scrollable box 'width' 500px = 'padding-left' 100px + ('margin-left' 50px + 'border-left' 25px + 'width' 300px + 'border-right' 25px + 'margin-right' 50px~0px) + 'padding-right' 100px~0px.
IE7: Scrollable box 'width' 650px = 'padding-left' 100px + ('margin-left' 50px + 'border-left' 25px + 'width' 300px + 'border-right' 25px + 'margin-right' 50px) + 'padding-right' 100px.
This is for the luxary of IE7 which doesn't quite cope with overflow:auto.
Containing block = 200px.
IE 7: Descendant block = ('margin-left' 50px + 'width' 300px + 'margin-right' 50px)400px.
IE 7: Scrollable box ('padding-left' 100px + ('margin-left' 50px + 'width' 300px + 'margin-right' 50px)400px + 'padding-right' 100px) = 600px.