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Internet Basics
   About the Internet
   About Web Browsers
   Why Domain Names

Getting Started
   HTML vs XHTML
   Making Webpage Files
   Naming Webpage Files

HTML Basics
   About HTML Tags
   Basic HTML Page
   DTDs and Doctype Tags
   Spaces and New Lines
   Special Characters
   Bold, Italics, More
   Writing Headlines
   Adding Links
   Making Lists
   Comments in HTML

Images and Colors
   How to Add Images
   Sources of Images
   Image File Formats
   Optimizing Images
   Color in HTML & CSS
   "Web-safe" Color Chart

More Advanced HTML
   Making Tables
   Formatting with Tables
   Making Forms
   Using Imagemaps
   Using Frames
   Meta Tags

Cascading Style Sheets
   Intro to CSS
   Ways to include CSS
   Some Useful CSS
   CSS Hover for Links

More
   Promoting Your Site
   How-To's Homepage
   Links

Domain Names and IP numbers

Every computer connected to the internet has a address. That address is called an IP number.

IP numbers are a set of 4 numbers between 0 and 255 separated by periods. 116.23.1.217 is an example of an IP address picked it at random. When I picked it there was no active webserver at that address. There may or may not be now.

These numbers are great for computers to use when they talk to each other, but most people have a hard time remembering them. For the use of humans, domain names were invented. WebStartCenter.com, MyISP.net, Nonprofit.org are all examples of domain names.

Hostnames and Subdomains

Sometimes there is more than one computer using the same domain name. These are distinguished by using host names. The host name is appended before the domain name such as www.webstartcenter.com or groups.yahoo.com.

Sometimes subdomains are used to create sub-sites using the same domain name, that may all be on the same server. These also look like support.myco.com or mail.yourserver.net, just like the host names. You can't tell from just the name which it is. If they have different IP numbers, they could be on different computers.

Virtual domains

Often more than one domain shares the same computer and IP numbers. These are called virtual domains. If you call these by their domain names, everything should work as expected. If you try to substitute in only the IP number for the domain, you might get unexpected results.

Domain Name Servers

Domain Name Servers are programs that store the information about which IP addresses are associated with which hosts. When someone registers a domain name, they tell the registrar the name or IP address of name server that will know where the site is.

When you enter a URL that uses a domain name in your browser, or follow a link that does, the browser will have to find out what IP address goes with that domain. It asks the domain name server configured in your internet connection to find out. If you have a functioning internet connection, then there is a domain name server it knows to consult. Usually it is one belonging to your ISP.

If 'your' name server doesn't know which IP address is associated with the domain, it asks a root nameserver. These have master lists that are updated whenever a change is made. Your name server will probably save the results it gets for a while, this is called caching.