alt Hacker NewsYes it varies. Using the QUERY method doesn't automatically mean your app is idempotent - it means the browser, and any intermediaries, can assume it's idempotent. So when you go forward and then back they're free to reissue the request and you won't get the "this may repeat whatever you just did" popup.
If it's not actually idempotent but you're telling the browser it is, of course you may cause bugs. Same as GET.
I think PUT, which is idempotent, would still require the "repeat action" warning, since it will overwrite any changes that happened to the same resource in the mean time (unless used with `if-match` or similar). QUERY won't require such warnings because it's safe, not just idempotent.