User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0b12pre) Gecko/20110205 Firefox/4.0b12pre Build Identifier: When opening a website that includes another in a frame and this second one does not allows being shown within a frame, instead of showing a message to the user explaining why there's no content and a link to open the website in another tab, it shows nothing. Reproducible: Always Steps to Reproduce: 1. Go to http://www.reddit.com/tb/fftxq 2. 3. Actual Results: Toolbar on top, white space on bottom Expected Results: Toolbar on top, message like Opera's: Error http://www.youtube.com/watch?v=3Ua10Jas7ak The website does not permit its content to be displayed in a frame. It must be displayed in a separate window. Load document in a new window

Reporter -> Are you still experiencing this issue with the latest version of Firefox 6? Does the issue occur with the latest nightly? http://nightly.mozilla.org/

I get the same "actual result" in Firefox 3.6 through the latest Nightly, Safari and with the latest Chrome. IE 8 and Opera show the expected result. This might be an RFE to generate an error page instead of a blank page when a site uses the X-FRAME-OPTIONS: DENY header.

This would at least make it clear what's going on.

Note that at this point IE is the only browser that does an error page for X-frame-options. Presumably this needs to be covered by a specification, since the difference between about:blank and error pages is black-box detectable by the parent page....

This bug bite me on Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:42.0) Gecko/20100101 Firefox/42.0 ID:20150806103224 CSet: 2fad09a0540d when visiting https://moz-test-page.herokuapp.com/

Similar bug for Chrome https://code.google.com/p/chromium/issues/detail?id=41251 Their X-Frame-Options is at https://code.google.com/p/chromium/issues/detail?id=467770