Usually it is hard to determine the usability of a website. But once we freeze on the usability of any website and with effective submission to search engines we are entitled to get a decent traffic from search engines.
Experts say that if a page doesn’t load in 8 +- 2 seconds then user doesnt stay in the site.Also experts say that a good UI design would make the visitors fixed / get what they intended to get. So while creating any website we atleast need to keep in mind the above two points.