Server Co-location (or Co-Lo)  is the process of placing computer equipment that you own in a secure web hosting facility.

All of the files for a web site are stored on a computer called a web server. These web servers are kept in a special facility called a data centre which has very high capacity connections to the internet and specialist power and cooling equipment.

The very vast majority of website are run on shared hosting accounts which means that one web server may run several thousand websites. But when a web site becomes busy enough, or if a very high level of security is required, it needs to be hosted on a dedicated server. In other words, a web server dedicated entirely to that one web site.

When an organisation has to go down this route, they have the option to either lease a dedicated server from a hosting company or co-locate their own equipment. A co-location contract covers the provision of space in a data centre for your equipment and the connection of this computer to the internet.

See 1U for more information about hosting racks.

A data centre is a secure building used by hosting companies to store their servers. They are usually specially designed secure buildings with sophisticated cooling and fire prevention systems, very fast connections to the internet and their own back up power supplies.

They store many thousands of servers in racks and hosting companies often build their own private rooms with in data centres. Each data cantre can host the computers of many thousands of different companies.

This is a web site hosting term that describes the amount of data that can be transferred to and from your web site. Most web hosting companies provide you with a monthly bandwidth allowance.

Every time someone visits your website, they will download all of the files required to display the page on their computer. The amount of data that has to be sent between your web site and the visitors computer is added to the amount of bandwidth you have used that month. Likewise if someone downloads a document from your web site such as a flyer or an application form the amount of data transferred is also added to your monthly total.

If the amount of data that you transfer exceeds your monthly allowance your hosting company will probably charge you an addition fee for each megabyte of information transferred.

All web sites have ongoing costs that they have to take into consideration. One of these is an annual or monthly charge for web hosting.

Web hosting charges can usually be broken down into storage space, bandwidth allowance and services such as databases.

The bandwidth allowance is the amount of data that you are allowed to transfer each month from your web site to you visitors computers. Each page on your web site may be about 20 Kilobytes and if you have 10,000 page views per month then you will transfer approximately 200 Megabytes of data.

Bandwidth theft is where another web site displays a file from your web site on their own web site. For example, if you have a nice photograph on your web site  that is 20 Kilobytes and another web site uses it on one of their web pages by loading the photograph from your server each time their page is displayed, this is bandwidth theft.

In this case they should either ask for your permission to download the photo and host it themselves or link to your page with the photograph rather than displaying it.