Actual results: Seamonkey 1.x rv: 1.9a1 build 2005090305, Deer Park alpha 2 rv: 1.8b4 build 20050903 and DOM inspector report that the computed css width of the table is 300px and DOM inspector also reports that the table offsetWidth is 500px. Somehow, -moz-box-sizing is set to content-box and can not be set to border-box: computed style -moz-box-sizing stubbornly retains, maintains content-box. This webpage layout is related to bug 96463: border widths are subtracted from table's intrinsic width and bug 155955: [BC] outer half of collapsed table border bleeds out of table box (border-collapse)

Expected results: the reported computed css width of the table should be 500px and its offsetWidth should be 600px.

1st col. & row2nd col. thead3rd col.4th col.5th col.
2nd rowtheadabcdabcdabcd
5th rowtfootabc
3rd rowtbodyabcabcabc
4th rowtbodyababab

The relevant CSS code in that page is
body {margin: 15px 100px;} #idTable { border-collapse: collapse; border: 100px ridge lime; width: 500px; -moz-box-sizing: border-box !important; } td {border: 4px solid blue;}

Reference: CSS 2.1 Section 17.6.2 Border-collapse model says: "Note that in this model, the width of the table includes half the table border"

Valid HTML 4.01! CSS compliant