Like most developers for the past couple of years I've been implementing form checking on a field by field basis so when a user is filling in a form field the client side error checking is run. This has a couple of advantages, firstly the users gets the errors there and then, so when they get to the end of the form it should be valid and ready to submit, also it's quite fun to implement! However, I was reading some research (which I have now temporarily misplaced!) which calls this approach into question. The basic premise was that in regard to form filling, the brain works in two different modes, the 'create' mode and the 'edit' mode.
In light of this the best way to handle forms is to allow the user to fill in the form (brain is in create mode) then validate all the elements in one go, so the user can go back over the form (brain in edit mode) to fix any errors. This was tested and found to be better than making the user switch from create to edit mode on a form field by field basis.
I'll try to find the relevant article, unfortunately my brain is in permanent 'confusion' mode so that may take some time!
