Forms - HTML and XHTML: The Definitive Guide - page 611

defined class of the <form> tag; its value is the name of that class. [ In-
line Styles: The style Attribute, 8.1.1 ] [ Style Classes, 8.3 ]

The lang attribute specifies the language used within a control, accept-
ing as its value any of the ISO standard two-character language abbre-
viations, including an optional language modifier. For example, adding
lang=en-UK tells the browser that the list is in English ("en") as spoken
and written in the United Kingdom ("UK"). Presumably, the browser may
make layout or typographic decisions based upon your language choice.
[ The lang attribute, 3.6.1.2 ]

Similarly, the dir attribute tells the browser in which direction to display
the control contentseither from left to right ( dir=ltr ), like English and
French, or from right to left ( dir=rtl ), as with Hebrew and Chinese. [ The
dir attribute, 3.6.1.1 ]

The popular browsers support the dir and lang attributes, even though
there are no behaviors defined for any specific language.

9.9.4. The tabindex, taborder , and notab Attributes

By default, all elements (except hidden elements) are part of the form's
tab order. As the user presses the Tab key, the browser shifts the input
focus from element to element in the form. For most browsers, the tab-
bing order of the elements matches the order of the elements within the
<form> tag. With the tabindex attribute, you can change the order and
the position of those elements within the tab order.

To reposition an element within the tab order, set the value of the at-
tribute to the element's desired position in the tab order, with the first
element in the order being number one. If you really want to change
a form's tab order, we suggest you include the tabindex attribute with
every element in the form, with an appropriate value for each element.
In this way, you'll be sure to place every element explicitly in the tab or-
der, and there will be no surprises when the user tabs through the form.