redirects urgent help please

I am having a major problem.

My site and my clients site are not opening via www.mysitename.com but will open via http://mysitename.com

does anyone know how i fix this? It is pretty urgent

 

Please upload file, index.htm & index.html .Home page is same.But, upload different ext.

 

Depends on what the DNS entry points too, for it to resolve correctly with or without the WWW both have to be listed in DNS.

http://en.wikipedia.org/wiki/Domain_Name_System

 

sorry ,i don't know ,hope someone help you ,good luck