how to create a database for a website in visual studio webdeveloper so that users can leave comments etc
Your question is too vague.
Sounds like you are going to develop this in asp.net in either vb or c#.
You will need a datasource and wil likely use MSSQL for your site.
The rest of the details will depend on exactly what you want.
Did you already create a mock up of the site with regard to the look and feel and work flow?
You need to think about authentication as well.