The onclick attribute on your anchor tag is going to call a client-side function. (This is what you would use if you wanted to call a javascript function when the link is clicked.)
What you want is a server-side control, like the LinkButton:
<asp:LinkButton ID="lnkTutorial" runat="server" Text="Tutorial" OnClick="displayTutorial_Click"/>
This has an OnClick attribute that will call the method in your code behind.
Looking further into your code, it looks like you're just trying to open a different tutorial based on access level of the user. You don't need an event handler for this at all. A far better approach would be to just set the end point of your LinkButton control in the code behind.
protected void Page_Load(object sender, EventArgs e)
{
userinfo = (UserInfo)Session["UserInfo"];
if (userinfo.user == "Admin")
{
lnkTutorial.PostBackUrl = "help/AdminTutorial.html";
}
else
{
lnkTutorial.PostBackUrl = "help/UserTutorial.html";
}
}
Really, it would be best to check that you actually have a user first.
protected void Page_Load(object sender, EventArgs e)
{
if (Session["UserInfo"] != null && ((UserInfo)Session["UserInfo"]).user == "Admin")
{
lnkTutorial.PostBackUrl = "help/AdminTutorial.html";
}
else
{
lnkTutorial.PostBackUrl = "help/UserTutorial.html";
}
}