Website Loading Time is Most Important Factor now a days. Users of the 21st century don’t like to waste 5 - 6 seconds during website loading. Website speed Also Affects Google ranking.
I think Best Time for Webpage Loading is 2 sec. I am Wordpress developer & i use it in most of my client websites. Wordpress is Best CMS [Content Management System], I wrote a white paper on Wordpress. You can read it Here