<blockquote> Security is not fine today. That is Firefox doing its job and telling you something is wrong with the Microsoft site. Hopefully it is a temporary relatively harmless misconfiguration, and not a sign that the MS servers and sites with copies of your emails on have been compromised. ---------- Further information To clarify use the threebar button top right. Next click on options (cog icon). Then use ''Advanced'' Look for the tab or panel ''Certificates'' Remove the tick by clicking the tick in the box in front of OCSP It is probably best to make sure that is back on again if you need to do anything important like banking, and of course once MS fixes the issue turn it back on permanently. -------- Alternative method ''cor-el said:'' {[/questions/1161934#answer-972795]} <blockquote> There seems to be something wrong on some Microsoft servers. Hopefully they fix this quickly on affected servers. This looks like a problem with OCSP stapling on the server because it works when I disable OCSP Stapling in Firefox. *https://en.wikipedia.org/wiki/OCSP_Stapling *https://blog.mozilla.org/security/2013/07/29/ocsp-stapling-in-firefox/ You can temporarily toggle this pref to false on the <b>about:config</b> page to see if disabling OCSP Stapling works for you. It is best to reset this pref via the right-click context menu to true once you are done with the this website. *security.ssl.enable_ocsp_stapling = false </blockquote> '''Please see also this article explaining how to use about:config''' * '''[[Configuration Editor for Firefox]]''' </blockquote> We have a contributors thread where you may be able to '''see the latest news on this issue''' * SEC_ERROR_OCSP_INVALID_SIGNING_CERT when I try to access my hotmail account. [/forums/contributors/712461]