In the OpenOLAT 11.5 release notes we announced that support for IE 8, 9 and 10 will fade out by the end of 2017 in OpenOLAT.
In the 12.3 release we implement the first step of skipping support for old browser by showing a warn message on the login screen when a user uses an old browser. The message can appear above the login form as a permanent message for those browsers. However, user can still use the system at their own risk. The browser check can be disabled using a css rule to hide the message in a custom theme if a client needs to use support those old browsers.
The idea is to prepare users for the hard cut in one of the following OpenOLAT releases where support will dropped entirely and login will not be possible anymore with old browsers. It is also a way to give clients the possibility to get into contact with us if support for old browsers is vital for them.
Implementation could be done by a simple conditional IE comment and a static text with a wrapper CSS class.