Do you already have a database? If so, use forms authentication and ASP.NET membership like everyone says. It is real simple to integrate into your current database (assuming it's sql server - i don't know about others). I realize adding a DB for 2 or 3 users isn't always an option due to budget or whatever so you can use forms authentication and store the user in the web.config. I've done this in the past and it is very simple.
Your web.config will look like:
<authentication mode="Forms">
<forms loginUrl="Login.aspx">
<credentials passwordFormat="Clear">
<user name="myUser" password="password" />
</credentials>
</forms>
</authentication>
Then you can use the built in login controls. If you do it this way you need to implement the Autenticate event.
protected void Login1_Authenticate(object sender, System.Web.UI.WebControls.AuthenticateEventArgs e)
{
string UserName = Login1.UserName;
string Password = Login1.Password;
if (FormsAuthentication.Authenticate(UserName, Password))
{
e.Authenticated = true;
}
else
{
e.Authenticated = false;
}
}
Of course this isn't the most secure way to go about this, and you'll probably want to at least look at encrypting the credentials in the web.config, but it is simple and works when a database isn't an option.