Robert_Charlton - 9:06 pm on Oct 2, 2010 (gmt 0)
However, most if not all adservers are called before the onload event, so those times definitely drag you down.
To get into a major-player specific here, not to out them but to understand what's going on... many New York Times pages seem to load their text quickly, but then there's a deadly pause... and by pause I mean that you might want to go and make yourself a cup of coffee... while the ads load. Rich media and Flash ads are the worst.
While they load, your computer is useless. The ads completely tie you up. You can't even read the page, because you can't scroll it. This, IMO, is what Google should be going after. But by this measure, many major online sites... not just the NYT... would be thrown out of the index (of course, that will never happen). But, is Google not seeing this? That's where the major disruptions come.
Candidly, I don't care much about the extra fraction of a second that many are shaving off their load times by streamlining code. What really hurts are back end times on dynamic pages, ad servers, and very occasionally a 2-Gb jpeg that someone has loaded onto one of their pages.