Comic Sans should never appear on the website; indeed, I haven't heard a single complaint about Comic Sans. I have Comic Sans installed, and it hasn't ever popped up. In the absence of any fonts, it should be whatever your Web browser selects as the default. The font stack is:

"Linux Libertine Display O", "Linux Libertine", "Liberation Serif", "FreeSerif", "EB Garamond", serif

I could stand to add in a common non-libre typeface.