I have no idea how to start. I need a database which allows users on a web site to get a user name and password, and then enter a description of an item and photographs. It needs to produce a new web page with a link from one central page. I have a mac so I need software to implement all of this. Can anyone either explain how to do this or give me some links. Also an idea of how many hours this will take to do. I am a quick learner! Thanks for your time.

You should definately check out HotScripts in the PHP section. You should be able to find a PHP login/usermangement script that you can download and implement quickly. Writing this yourself if you don't know mySQL or a server side scripting language like PHP or (ASP if your server is Microsoft) would take a very long while of trial and error and then you have security issues that you wouldn't even know the first thing about. If you do WANT to learn this stuff, by all means go ahead. I'm still in the process because the projects that I'm working on all have no deadline so I have the time and the patience to do so. Here are some places to start, although I do recommend getting some books on the subject, there's just so much web reading that one person can take.

http://www.php.net
http://www.phpbuilder.net
http://www.sitepoint.com