The Netscape-derived legacy Crypto API implemented on
window.crypto has been removed, including
version properties as well as
signText methods, in favour of the standard Web Crypto API. See the MozillaWiki article for details.
This legacy API has been disabled with Firefox 33 but enabled again with Firefox 34 because various banks and government agencies were still using it. Now the API has been completely removed but Firefox users who still need to use such sites can install the signTextJS extension alternatively.