(1) The Magnolia AdminCentral UI uses a custom web-font.

(2) Following the OWASP recommendations, the caching headers are set as follow in the Apache:
(https://www.owasp.org/index.php/OWASP_Application_Security_FAQ#Browser_Cache)

Header merge Cache-Control no-cache env=NO_CACHE
Header merge Cache-Control no-store env=NO_STORE
Header set Pragma "no-cache"
Header set Expires "Wed, 10 Jan 1970 00:00:00 GMT"

(3) Unfortunately the IE has an issue with webfonts under these conditions:
(https://connect.microsoft.com/IE/feedbackdetail/view/992569/font-face-not-working-with-internet-explorer-and-http-header-pragma-no-cache)

(4) Steps-ToReproduce:

• use a setup as above
• use InternetExplorer
• load AdminCentral page / press F5 or CTRL-F5

—

Request:
The AdminCentral UI should have a working font fallback that allows continuing to work even when the WebFont can not be loaded. (font & icons)

Looks like there is no fallback set - therefor the IE 11 decides to fallback to TimesNewRoman font and the "icons" can not be loaded.