I have just register a web hosting account. can i access my Web site right after registering a account.

U can make a Temporary Index Page for that
To do this, you will have to use an instant domain alias . Instant Domain Alias is an additional web address which lets you access your site during the first several hours after the domain name registration, the time when the site is yet unavailable at the newly registered domain. Over the next few days DNS servers all across the Internet will update themselves with your new site name. Once that happens, you will be able to access your site at the domain you have registered.