First Impression
The first thing a visitor will notice about your website is how quickly it loads. If it loads quickly, they might not think about it; but if it loads slowly they will think about ti. And possibly, if it loads really slowly, they might leave your site and try someone else.
Because Google Cares
Google is increasing rewarding websites that load quickly and penalizing websites that load slowly. Now, this is not the only ranking factor, but it is one more thing that can either help you or hurt you.
Mobile
More and more people are browsing first from their mobile devices. So not only is it important to have a responsive site, but that your website loads quickly. Because mobile users can often be in places where they don’t have the greatest connection, it is all the more important that your website load quickly.
How Do I Know
Pingdom has a cool tool that checks how quickly your website loads. GTmetrix is another website to check out. Enter which city you want to test from and it will show you how fast the different parts of your website are loading. Some of their recommendations might not apply to you, so talk it over with a pro.
How Fast
Ideally your website should load in under 2-4 seconds. The faster the better.