A CDN stores a copy of your website in multiple locations "in the clowd" to make it load faster.

They say you learn something new every day. However, I am embarrassed to admit that even though I’ve been blogging for some time and had been writing about SEO for some time, I’d never heard of a CDN until John Chow mentioned on his blog that he uses one and that it’s part of his monthly expenses. Here’s why a CDN is vital for your blog or website:
What is a CDN?
Fair question. I hadn’t heard the term myself in spite of having installed and configured W3 Total Cache, a WordPress plugin I recommended a while back. In essence, CDN stands for Content Delivery Network. It’s a way to make your website or blog load faster. In some cases, much faster simply because of the way it’s delivered.
How an Ordinary Website Delivers Content
Wherever you happen to have your website hosted, it’s located physically on a computer somewhere in the world. That somewhere could be in the USA, it could be in Pakistan, it could be in Timbuktu. When someone visits your website, the material is fetched from the server and bounced through a number of nodes before it gets to your visitor.
The further away your visitor is physically from where your blog or website originates, the longer it takes for the material to bounce around and get to where it’s going. In the early days of the net, the difference used to be profound, with local sites loading up as many as five times as fast as far away ones. These days, the difference is a matter of seconds, however seconds matter.
Google Indexing and People Clicking Away
A slow loading site means that people will click away because your website doesn’t load up quickly enough. This means directly lost sales for you. In addition, if your blog or website loads too slowly for Google’s bot to crawl it, the system will just give up and move on to something else, resulting in loss of ranking. A CDN changes all that.
So How Does a CDN Work?
Put simply, a CDN will set up a copy of your blog or website at locations all over the world and serve it up transparently to your users from the server closest to them. The result is faster load times and a smoother experience for your readers. Ultimately, this means more traffic for you and more sales for your business.
How to Implement It
The first thing you need to know about is how to implement a CDN. It’s actually pretty simple. Most CDN services come with instructions. It’s usually a matter of using a software caching program (such as W3 Total Cache, which is why I felt like such a dunce for not noticing the CDN set up features) and simply entering your information.
What Does It Cost?
CDNs, like web hosting and other services vary in cost widely from one service to the next. The one I’m using is the one John Chow recommended – MaxCDN. They’re running a special right now for $39.95 for a terabyte of transfer for one year. For most small blogs and websites, this should cover you for the whole year.
Plus, use the coupon code John Chow and you’ll get another 25% off on the cost of the CDN service (and no, I don’t have any affiliation with John other than being a fan of his blog and having learned a lot from reading what he has to say. However, I doubt he even knows who I am).