I recently ran into a situation with a custom form where users had a number of checkboxes where the values were saved upon submit. When they went back through the form to make changes, if they unchecked something that was already checked and submitted the form again, the checkbox value would not change (not empty). The solution (thanks to Demitrious for finding this!) was simple.
Ever wonder how to get a mouse over “tool tip” to appear without much hassle? Use the title attribute (keep your mouse over the link for a few seconds to see this in action). Not only does this help your users/readers get more information, it also helps people who are using auditory browsers will have the title information read to them. Not all links should use the title link, but if you want to provide additional information to your audience, give it a shot. Be aware that different browsers treat the title attribute differently.