markosweb's answer works. You just have to wait a while before the changes take effect. Thanks!
I tried the suggestion below by markosweb (June 5, 2014).
Error: CNAME records cannot share a name with other records
I'll try the other method with .htaccess file.
If it is a wordpress installation, you also need to make sure that the siteurl for the wordpress website starts with www, else you will get the same problem.