ASP.NET username/password security
<p>I'm using VS2010,C#,SQL Server to develop my ASP.NET web app, although this is not my first ASP.NET experience, but this time my project is more attack-prone and I should consider better security polices. I have a login screen as my first page, users enter their user name and password and a page specific to them is showed, in my last project, I used query strings (a userid) along with sessions for security purposes, but this time I've used just query strings, it means that at the moment one can enter myaddress.com?userid=1 and visit a page in my site!!!
I know this is not good, but what are my approaches, of courses I'm not working with banking or financial systems but I'm going to have an standard security policy, I should use sessions? cookies? can you suggest me an easy-to-develop and meanwhile secure way of implementing protection policies? any sample code or tips?</p>

<p>thanks</p>
