After http://trac.webkit.org/changeset/43355, the three text inputs in the middle of the page wrap when they shouldn't in Windows WebKit. The problem is that we match IE widths for the inputs, but then have extra margins that cause the three inputs to not fit on the line. There's a couple things we could do to fix this: 1. When we have intrinsic margins, make inputs/textareas correspondingly smaller. 2. Use the IE margins on inputs/textareas and live with them looking somewhat less pretty. 3. Always make inputs/textareas smaller by the fixed amount that we grow intrinsic margins by. 4. Live with the incompatibility and try to contact the americanexpress.com webmaster to fix their site. It's not clear to me what the best choice here is.
<rdar://problem/6989388>
As best I can tell, this has been fixed on the americanexpress.com side. They've added CSS widths to the text inputs.