Fill the "conta" textfield in the top of the page with 4 numbers (0000) then hit Tab to go to next textfield, then an alert will be shown saying that you must type only numbers.
Confirmed with a local debug build of WebKit r21856 with Safari 2.0.4 (419.3) on Mac OS X 10.4.9 (8P135).
Also occurs with shipping Safari on Tiger (see versions above).
Not only does it intercept tabs, but also Cmd-W and Cmd-Q!
Works in Firefox 22.214.171.124 (tab, Cmd-W and Cmd-Q).
Needs a reduction to determine if this is actually a WebKit bug or whether the site needs evangelism.
See also: bug 13031.
Created attachment 17673 [details]
Working on a fix.
Fixed in revision 28620 - we now match IE and no longer dispatch keypress when tabbing between input fields.