I have a link in my HTML:
<a href="/DoSomethingDangerous">do something dangerous</a>
Visiting the DoSomethingDangerous link causes a not easily reversable action to occur.
So after the link is clicked on I would like a dialog box (eg "Are you sure?" "OK" "Cancel") to be displayed and if the user clicks Cancel the link is not visited and the browser remains at the same page.