My facebook app renders blank for some users <p>I have built facebook app. It's hosted on: <a href="http://resihop.herokuapp.com/" rel="nofollow">http://resihop.herokuapp.com/</a>.</p> <p>The app is suppose to be visible here: <a href="https://apps.facebook.com/393963983989013/" rel="nofollow">https://apps.facebook.com/393963983989013/</a></p> <p>On facebook it's embedded in an iframe. The weird part is that for some users the content of the iframe is empty, just: and for some users it displays the page. Here is the html: that I got from inspect element:</p> <p>Working:</p> <pre><code>&lt;div&gt; &lt;noscript&gt;&amp;lt;div class="mas"&amp;gt;&amp;lt;div class="pam uiBoxRed"&amp;gt;Du måste ha javascript aktiverat i din webbläsare för att använda Facebook-applikationer.&amp;lt;/div&amp;gt;&amp;lt;/div&amp;gt;&lt;/noscript&gt; &lt;form action="https://resihop.herokuapp.com/?fb_source=search&amp;amp;ref=ts" method="post" target="iframe_canvas_fb_https" id="canvas_iframe_post_4fe8ad942b9be6531902412" onsubmit="return Event.__inlineSubmit(this,event)"&gt; &lt;input type="hidden" autocomplete="off" name="signed_request" value="x4b_ddxAkL71eQEdopzIZJpWZCmTPFqOMmmMvx_TCC8.eyJhbGdvcml0aG0iOiJITUFDLVNIQTI1NiIsImV4cGlyZXMiOjEzNDA2NTQ0MDAsImlzc3VlZF9hdCI6MTM0MDY0ODg1Miwib2F1dGhfdG9rZW4iOiJBQUFGbVR1TlI2UlVCQU9zQkRkc2hwbkpNN0pKR0ZaQTNsaGhtMlViNWFlWkFpeFpDNnNYcWVEbXpaQjVqb1dtVUwzVTg1WW5wUWg2WkJVdUxQV3o2M1lIQk5aQVQ4a3dNNGNtWkExZU00MXZ5SU5KeVpDeWFpbDhWIiwidXNlciI6eyJjb3VudHJ5Ijoic2UiLCJsb2NhbGUiOiJzdl9TRSIsImFnZSI6eyJtaW4iOjIxfX0sInVzZXJfaWQiOiIxMDAwMDA2MjcwMTQzODQifQ"&gt; &lt;/form&gt; &lt;iframe class="smart_sizing_iframe" frameborder="0" scrolling="yes" id="iframe_canvas" name="iframe_canvas_fb_https" src='javascript:""' height="800" style="height: 574px; "&gt;&lt;/iframe&gt; &lt;/div&gt; </code></pre> <p>Broken:</p> <pre><code>&lt;div&gt; &lt;noscript&gt;&amp;lt;div class="mas"&amp;gt;&amp;lt;div class="pam uiBoxRed"&amp;gt;You need Javascript enabled in your browser to use Facebook Applications.&amp;lt;/div&amp;gt;&amp;lt;/div&amp;gt;&lt;/noscript&gt; &lt;form action="https://resihop.herokuapp.com/" method="post" target="iframe_canvas_fb_https" id="canvas_iframe_post_4fe8adec0223e0f59580030" onsubmit="return Event.__inlineSubmit(this,event)"&gt; &lt;input type="hidden" autocomplete="off" name="signed_request" value="yx5eMWJ-0WFSOHg5bkfxesurLc5zZcfuYdyuJqffv0M.eyJhbGdvcml0aG0iOiJITUFDLVNIQTI1NiIsImV4cGlyZXMiOjEzNDA2NTQ0MDAsImlzc3VlZF9hdCI6MTM0MDY0ODk0MCwib2F1dGhfdG9rZW4iOiJBQUFGbVR1TlI2UlVCQUJ6NVRxdWRuaW1tN01ZVzRkdXhSMHczTU1zcDZvbU9ZZ3ZZVm1zZG11dVJLN1lEb1h6Mm9TYUFIeUpaQ2NsSjg5cFBFWkJaQ2haQURyMGZCWWIxOUxaQ0o0QnVaQnR3WkRaRCIsInVzZXIiOnsiY291bnRyeSI6InNlIiwibG9jYWxlIjoiZW5fVVMiLCJhZ2UiOnsibWluIjoyMX19LCJ1c2VyX2lkIjoiNjUxNjY2NDgzIn0"&gt;&lt;/form&gt; &lt;iframe class="smart_sizing_iframe" frameborder="0" scrolling="yes" id="iframe_canvas" name="iframe_canvas_fb_https" src='javascript:""' height="800" style="height: 294px; "&gt;&lt;/iframe&gt; &lt;/div&gt; </code></pre> <p>One difference I have noticed is that the actions are different. I have waited for several hours now, so it might be a server-unsync-thing, but probably not.</p>