Last modified: 2013-12-27 13:52:27 UTC
With SF 2.4, I just tried {{{standard input|cancel|label=Clear form}}} on a Special:RunQuery form, and discovered the button does not even display. The button would be useful for clearing a form for a user to start over, especially on large or complicated forms. I was able to work around this shortcoming with the fullurl magic word and a very large query string to create a link that explicitly blanks all form parameters. Without the query string, some browsers will keep the data loaded in the fields.
I assume you mean "reset", as opposed to "cancel".
Now that I think about it, it would be better to create new standard inputs that can be used on all forms, instead of just co-opting "cancel" only for Special:RunQuery forms. In that case, I would expect a "reset" standard input to reset the form to its original, preloaded condition. And, a "clear" standard input would blank all fields. So, I suppose that's 2 different new standard inputs needed to cover both resetting the form, and for clearing it.
Setting this to "wontfix" - I think "reset/clear" buttons in forms are generally bad; I agree with this: http://www.nngroup.com/articles/reset-and-cancel-buttons/
