Comic sans is a joke, yes, but all things have its useful place [csszengarden.com].
Its like colors, who would actually use pink and brown together 10 years ago? Tody its the trademark of a "hot designer who dares to break traditions". Some day you'll see comic sans all over the elit designer creations. Today a joke, tomorrow a trend.
I still remember the day I saw a place named "Hobo Barbeque" and the name was painted on the building in, you guessed it, the Hobo font. :)
And the answer to the question is it displays in the default font. Most browsers default is Times but I have seen people fax in a page from my site and they overrode all font settings to be Zapf Chancery. I didn't even recognize my own page. :)