Why are some buttons are blank in IE 10? (Specifically, buttons with glyphs in the private use are blank)

[ben363]

Some buttons are coming up blank.

It happens for IE 10, not for Firefox or Chrome.

And it only happens for buttons with high numbered (private use area) glyphs: for eg icon-share is OK (unicode 27a6); icon-search-thin, icon-export, and icon-print are not (unicode: ec68, ec89, ecc2).

If I turn off https, the problem goes away, but this is not an acceptable solution.

[ben363]

Adding the site to the list of trusted sites fixed the issue.

[LukeMurphey · Accepted solution]

I have seen this happen when IE is running in restricted mode. Adding the site to the list of trusted sites will fix this (assuming this is the same issue).