Breakdown of a URL

Introduction

Buying a domain name is easy, you take a credit or debit or credit card, you part with anything from a few dollars, and you have a domain name, no matter who you are.  But spoofing domain names is easy too, and how is the domain name composed.  is www.yahoo.com the same as yahoo.mysite.com ?  Which one is valid, which one is illegal?

Take one of my URLs

http://forum.helpbytes.co.uk/viewtopics.php?ID=344&Forum=1

http://
This part is the protocol.  http is the hypertext transfer protocol, and is the standard for transmitting webpages over the internet.  This protocol is assumed by default in most browsers, hence why you don't need to type it.  Other protocols commonly used are ftp:// and https://.  https:// is a secure, encrypted version of http, often used when making payments, doing banking or submitting confidential details over the net.

forum
This is called a subdomain of my domain name helpbytes.  It represents another section of my site.

helpbytes
This is my domain name, which you can say is a subdomain of the co.uk.  This is how my webpages are known, it's the name I chose.

.co.uk
.uk is a ccLTD (country-code TLD[top level domain]).  .co is a subdomain of the .uk TLD.  This is common in some ccTLDs, such as .org.uk and .me.uk.  .com and .net at the end are known as gTLDs.

viewtopics
This is a particular webpage.  This is the page that you are requesting to view on my website. 

.php
This is the file type BUT IT MEANS NOTHING!.  I could name it .jpg, but the browser will be told its a php page and still output the same, not an image.  So .txt doesn't always mean a plain file, it could easily be an exe file.

? Some webpages need parameters, such as dynamic web pages.  They will all follow the ?.  Parameters are in the form name=value and are separated via an ampersand (&).

www.

www. is also a subdomain, just like forum in the above example.  www. is often used to show that the contents are webpages, www standing for world wide web.  Many sites now are accessible without the www.
At one time, if no other subdomain was present, www. would be to denote the contents as being a webpage.  The same as the users FTP server would be ftp.domainname and their e-mail server would be mail.domainname.  But today this is not always as common, as many servers run all the services on one IP, and it's just as easy for the domain name by itself to access every service!

Tricks

Don't be fooled by what you see.  The text you click can be called anything, the domain name is in the underneath code:
For example, www.google.com might look in text as though you're going to google, but click it!  The HTML code says go to www.yahoo.com but make the link www.google.com. Hovering over the URL will reveal the real URL in your status bar.

Chatrooms

URLs posting in chat room are often not in the same form as HTML. By this I mean you can't give the link a name like I did in the first trick above.  So the URL you see, is the URL you will get too. Any funny codes indicate something is going on, and ignore it.

Conclusion

It is safe to click most links if you know the content, or the source is safe. If you really want to be 100% safe of spoofed URLs, type the URL in yourself, or if you know HTML, view the source of the page and check it out.