We don’t have much patience, if any at all, when it comes to waiting for a page to load. In fact, users want a site to load in a matter of milliseconds. According to Harry Shum, a Microsoft computer scientist, users will visit a website less if its loading time is slower than its competitors by 250 milliseconds, or one-quarter of a second. That is less time than the blink of an eye.
Boost Search Engine Rankings
Fast and optimized websites lead to higher visitor engagement, retention and conversions, but page load times have become significantly more important now that they help to determine your website’s search engine ranking.
Until recently, Google determined page rank using two primary factors: relevance (how pertinent a page is to the actual search) and authority (the number and quality of inbound links to a website). In their continued quest to improve user experience on the web and deliver useful search results, Google decided to modify their search ranking algorithms to include site speed as a determining signal.
Why has Google become obsessed with speed? The following excerpt from Google's blog emphasizes how important page load times are on the Internet:
"At Google, we focus constantly on speed; we believe that making our websites load and display faster improves the user’s experience and helps them become more productive."In other words, an optimized website is fast and makes users happy. If your site’s not fast, it can affect its overall ability to rank well on search engines. Obviously, Google has tons of ranking factors and site speed is merely one, but every little bit helps right?
Lower Operating Costs While Increasing Revenue
Still not convinced? If SEO isn't your goal, think of conversion rates.
When a site responds slowly, visitors spend less time there. If a user gets frustrated and leaves your site, your conversion rate drops. The slower your site is, the more potential customers you’re likely to lose.
Users aren’t used to waiting and expect they won’t have to. They have the luxury and ease of finding comparable products and services on another site, namely, your competition.
The bottom line is, faster sites create happy users and happy users become happy customers. Give the users what they want... it’s a mutually beneficial relationship.
 Lohr, S. For Impatient Web Users, an Eye Blink Is Just Too Long to Wait. New York Times. 26 February 2012.