For overall usability of a form you must make it easy for your visitor to know they are making the right choices. Anything that can confuse the visitor is bad. Just because you know what to press doesn't always mean your visitor will.
Badly formatted forms will actually do you more harm than good. It is surprising to think that this basic concept is missed by so many E-Commerce sites that rely on form filling to get your cash.
So if you want to have the edge on the competition get your form writing skills up to date and watch the cash roll in (well maybe not but you know what I mean )
When laying out your forms you must pay attention the the placement of text that relates to the form element.
Following the above rules, in addition to adding the accessibility tags will make your form more friendly and usable for everyone.
So, now that the general rules have been explained, let's look at the accessibility form tags in more detail.