No, you and your visitors can access your main page and all pages on your account either with or without the "www-dot" prefix.
On our servers, as with most servers these days, one can access the index page on a given domain by entering the domain name without the www. however, as over the years so many users have gotten into the habit of using the www., and enter it automatically, our servers are setup to recognize your domain name equally well either with or without the third-level domain "www".
Both of the following will resolve to your account's index page:
Things to Note
Subdomains are the exception to this rule. To access a subdomain one must enter the subdomain URL in the format subdomain.domain.com.
- http://subdomain.domain.com will work
- http://www.subdomain.domain.com will not work