Hello,
when I look it in the inspector of Coda 2.0 (the editor I use), which is Webkit based, it says "table.ui-datepicker-calendar 1946px x 170px".
When I check the same line with FF Webdeveloper tools it says nothing about the width, the css says width: 100% here.
In the tree there's a clear before, so the only instance above is body with a width of 1205px.
So I have no idea where these 1946px are coming from

What the hack is Apple doing here?
cheers
quwax