I think we could do: 1. for stepDown(), we set the value to max if it exists, to stepbase otherwise; for stepUp(), we set the value to min if it exists, to stepbase otherwise. 2. for stepDown() we set the value to stepabase - step; for stepUp() we set the value to stepbase + step. 3. for stepDown and stepUp() we set the value to stepBase. Chrome's behavior is a mix between 2 and 3. Opera's behavior is 1. Maybe UX should be involved there.

I think this is too low-level for UX, based on past experience. I would vote for 1.

Note that the spec now defines the behavior here: http://www.whatwg.org/specs/web-apps/current-work/multipage/common-input-element-attributes.html#dom-input-stepup Where it says: If applying the algorithm to convert a string to a number to the string given by the element's value does not result in an error, then let value be the result of that algorithm. Otherwise, let value be zero. So we should use zero.