In IE go to view/text and make sure the size is set to medium. Something like this usually effects non pixel based fonts. If that didn’t work then you might try deleting the IE user registry settings. If not then the corruption is more involved and requires setting up a new profile. You may also test the website under a different profile to confirm that the problem is user based.
HKCU/Software/Microsoft/Internet Explorer.
Delete the Internet Explorer folder and re-launching IE should rebuild the user settings.
Probably want to backup the registry first