Digital signature support in Firefox 35 and newer
In Mozilla Firefox 35 digital signing function has been removed. This breaks many sites that use signing in the browser.
In order to fix this problem the following add-on - signTextJS must be installed from https://addons.mozilla.org/firefox/addon/signtextjs/.
Add-on installation is not necessary for web sites that Java applets for signing, such as National Revenue Agency and Commercial register of Registry Agency.