Are you are going to run this at your house or office on some type of high speed connection such as cable or DSL? If so, here are a two other things you will need to consider. One is whether you will have a static IP address and two is whether or not your ISP will allow you to host a website on it for the level of service you are on. To explain further.
When you purchase your domain (such as yourcompany.com), you will need to have someone setup DNS to point
www.yourcompany.com to an IP address. The IP address is like a mailing address and tells other computers where to go on the internet. DNS is used to convert the friendly names such as
www.yourcompany.com to an IP address. Some registrars have DNS services built in, such as register.com. Many people will have their ISP do it for them, often at a price.
Some ISPs give their users static IP addresses, as in they won't change. It will be assigned to your location and will identify you on the Internet. Most ISPs will give out dynamic IP addresses for their residential customers. In that scenario they will have a pool of IP addresses and you will be assigned one every time you login or connect to the Internet. Those can and will change.
Typically you will be hard coding the
www.mycompany.com to a specific IP address in your DNS service. To do that you will have to make sure you have one that doesn't change. Many ISPs will offer (incorrectly named) business class services on DSL or cable that will give you a static IP address.
If can't afford that or it isn't available and you have a dynamic IP address, then you will need to use a dynamic DNS service, such as dyndns.org. Those will be setup so that something called the time to live (or TTL) is very short. This makes other DNS servers not cache the data for a very long time. It will require more lookups to your DNS provider, but with that you can safely change IP addresses and not have to wait a day for the rest of the Internet to know about it. You will then run some type of client on your computer that will automatically tell DNS service if you have a new IP address.
Finally, I've been told by some friends that some ISPs (Time Warner specifically) will block port 80 from their residential users to the Internet. What that basically means is that you will have your webserver up and running, but the rest of the Internet will not be able to connect to it. You will need to call your ISP to find out if that is true in your case. IF so, then you may need to upgrade to a business service to allow you to host the site.
As an easy alternative, however, you could purchase a webhosting service from an outside company. They will have webservers setup at their location, usually with a very fast connection to the Internet. On each machine they will host multiple websites. You will be given a space to place all your files and some method of uploading the files, such as FTP or Frontpage. You will pay a fee of something like $20/month for the service. In that scenario, you will only need to create the website and upload it to their servers.
Hope that helps