There’s an interesting article here about validating user input, and the usability implications of doing so. It outlines several methods (I suppose they could be classed as patterns) of doing this and notifying – or not notifying – the user.
This was found through Harry Fuecks article on Sitepoint, where he says that there’s no real alternative to regular expressions. He’s right, of course, and over the last couple of years my use of regexp’s has increased so much that rarely does a day go by when I’m not messing about with them. However I’ll be referring to the list of “validation patterns” (as I’ll call them) as it provides a useful reminder of the different ways that user input can be handled.