One of my CSS rules does not show up at all in developer tools in ie8 (it works fine in normal browsers). Not even with strikethrough. 
I checked the CSS file through the browser and the rule is really there

What could be going on here and how to fix this?
Why don't I drop support for ie8 altogether?
Just for those who wonder:
I recently worked for the Dutch government and they're still on Windows XP. They recently paid Microsoft for prolonging support by another year or so. They have their computers locked against installing anything (Firefox, Google Chrome) so they basically force employees to use ie8.
As we speak, some 6% of all visits to my site are by ie8. My guess is that many of those are involuntarily on ie8. Dropping support will bother them but really won't help them to upgrade to a proper browser.