Unique IP Address
As we mentioned before, web servers have a static IP address that rarely changes.
However, that does not necessarily mean that your site will have a unique or dedicated IP address!
If, like most people, you have opted for virtual hosting, your web site is stored on a computer along with several other sites.
Because of the relative scarcity of IP addresses, your web host may have assigned only one IP address to the server; this means your site shares the IP address of the server with the other sites stored on it.
In practice, this is rarely a problem. Modern browsers send "header information" to the web server; it contains, among other things, the domain name of the requested site.
Based on the header information, the web server is able to return the right data to the browser. (This is the "name-based virtual hosting" we referred to earlier.)
Some web hosts offer a unique IP address as part of their hosting packages; so even if a web server hosts several sites, they will all have different IP addresses.
There are only a few reasons why you would really need a unique IP address, like running your own mail server (an application that we feel is outside the scope of this introduction to web hosting), or having a unique secure server certificate for your domain name.
Having a unique IP address may offer some additional benefits. For example, it is sometimes rumored that search engines may punish spammers by completely ignoring their IP addresses.
We're not convinced that this rumor is true (many innocent site owners would be punished in addition to the spammers!), but if it is, having your own unique IP address could ensure that you are not punished for the actions of a spammer hosted on the same computer.
Another advantage is that even users with really old (or obscure) browers could visit your site. Name-based hosting only works with browsers that support the HTTP 1.1 protocol —but that's just about every browser released since 1996!