Hi Guys

Just wondering why some websites don't have the www prefix ?

What are the advantages and disadvantages of this ?

There are no advantages or disadvantages. Some webmasters like the www in front of the domain - others don't. But they have to keep it consistent.

Hole in 1.

You can also use Google Webmaster Tools to choose what is displayed in the search results, www.example.com or example.com.

that's right... i always configure my .htaccess to redirect all http to www. it's just my personal choice.

http and www are two different things.http is hypertext transfer protocol which is protocol which files have to follow when they get transfer..whereas www refers to the world wide web i.e the entire internet connection on planet