Web designer may be the one who design the appearence of webpages.
Web developer is to develop the complete web site, including the functionalities, cgi, database, etc.
But I find people always get confused with the above two, even some employers who are looking for new employees.
After a web site is developed and put into use, it's the Webmaster's job to maintain the server, keep the message updated, etc.
Please point out any mistakes, thanks.