Error trigger: it’s a known feature of Chrome 10, if required is present in input [1].

Solution: use formnovalidate in whatever button that triggers the prompt [2], or simply use novalidate in form tag. Either one is sufficient.

<form action="editor.cgi" method="post" novalidate>
 <input type=submit formnovalidate name=save value="Save essay">
 <input type=submit formnovalidate name=cancel value="Cancel">
</form>