Well, before things can be explained further, you need to decide what language you want to use, I did recomend you PHP, however, I don't think thats a great idea anymore.
I use ASP, so I'll explain it that way...
I really doubt you have a SQL Server? If not, don't worry about it. Have you ever used/heard of Microsoft Access? I think you will have, this is ideal to use a database back-end for your project.
Quite simply, each page that user is required to interact, the database will be contacted.
Register Form - You'll need one of those so people can get themself a username/password. This will be a form, that interacts with the database, to insert the relavant information.
Login Form - This will check a submitted username/password with ones in the database, and if it is then it'll send you to...
Post Form - The place where someone types up what they want to submit, also added to the database.
Display - Show what they have submitted.
Something you really, do, need to understand is what a RecordSet it is. It's basically, information from a database, held in a web page.
This is where the filter comes in. You want to display one submission, as if it has it's own page. With ASP, one page can be made, but it has the ability to fliter out the ones it doesn't need, and only display the required one.
I can help you with this if you like, but I need to know... does your host support ASP and Access? If not, do you mind moving to a free one?
If you do want my coding help, then, simply make the pages, in a way you see fit, with the forms etc, and I'll add the ASP to make it all work.