Is it happening on multiple PCs or just one? You said IE what version of windows(IE has been replaced by Edge)?
Font’s can work differently on different machines. You have a CSS font-family element that will suggest more than dictate what font a browser will use.
font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
Ask’s the browser touse "Helvetica Neue" if it’s installed, if not then use Helvetica, and if that isn’t available, then try Arial, and so on, from left to right.
The browser can also have a style sheet that overrides everything that you say. The user is in ultimate control.
What’s strange is you are getting a serif font, not a sans-serif. If it’s a machine you have access, then the only way to say for sure is to use the developer tools in the browser.
I don’t have a windows machine at all right now to test it out. But if you want to post a URL, perhaps someone here on the forum could test it for you.