"font-family: monospace, monospace"
CssMonospaceNormalize CssCss Problem Overview
In normalize.css, the monospace font rules contain
font-family: monospace, monospace;
Is this different to
font-family: monospace;
?
There must be a reason for using that. Maybe it's a workaround for the behaviour of some browsers?
Css Solutions
Solution 1 - Css
You are right. The font-family: monospace, monospace; declaration is a simple hack/workaround for some browsers which tend to reduce the font size of monospace fonts.
More info on this Github issue: https://github.com/necolas/normalize.css/issues/519#issuecomment-197131966
Solution 2 - Css
Yes, this is a workaround for a long-standing (I'm talking over a decade) issue with browsers' handling of the monospace generic family. Eric Meyer has a detailed write-up on this, and I explored this recently while answering this question that's specifically about Firefox's handling of monospace fonts.
Why does it work? How is monospace, monospace different to just monospace? Nobody knows. I made a guess based on Firefox's behavior, but it's just that: a guess. But one thing is clear: monospace, monospace is recommended over just monospace if you don't want to deal with this behavior.