Nobody used white as default, but sites that explicitly set their background color used white quite often. Here's a site that I made for my dad's real estate project back in 1997:
(The snapshot is from May '98 which is when the Wayback Machine first discovered it, but I built the site earlier than that)
The background color was actually a point of contention. I thought the default gray looked better, but my dad's perception was that most big professional sites seemed to be choosing white, so we went with white as well.
Was it that the backgrounds were gray, or that the default browser background was gray and no one set bg colors? I remember thinking the weirdest thing about IE when it came out (or was it another browser?) was that all the backgrounds were suddenly white.
The default in the browser was gray. White looked wrong when browsers started to have that default, because the 0000ff blue links were too bright against it. Since then a lot of sites have grayed down their link color to compensate.
