The 404 error signals no page found
In which case the page you wanted wasn't available at time u requested it, if after a couple of refreshes it still not availbale, its probs not there due to the server being down.
Of course miss typing a website address usually produces same affect, if what u mistyped doesn't exsist and also a site address thats been changed and not redirected properly can also do this.
Hope That helps ya.
'Keep it Kool
'