Thanks for the replay

below is the controller code

currently i am using 3 profiles  i am calling the methods saparately as shown below the problum hear is i am unable to login to the portal

currect 'cs3.salesforce.com' is the domain for the non-sites page. it is the domain of customer portal ,  i am trying to point out to the customer portal using salesforce.com pages .

below is the My page and controller

page

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<apex:page showHeader="false" title="KBR Capital Partners" controller="kbrLogin" id="page">
<apex:includeScript value="{!$Resource.commonjs}"/>

        <h1> Investor / Advisor Login</h1>
   

<apex:pageBlock id="pblock">

  
               <apex:form id="form">  
            
                      UserName: 
                 <apex:inputText value="{!username}" id="username1"/>
                   
                        Password:

                       <apex:inputText value="{!Password}" id="username12"/>
                        
                <input type="image" src="{!URLFOR($Resource.LOGINBUTTON)}" id="Login1"  onclick="{!login}"/>
          
              </apex:form> 
  </apex:pageBlock>
  </apex:page>

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controller

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global class kbrLogin {

    global String username {get; set;}
    global String password {get; set;}

    global void getlogin() {
    try{
       User u = [select ProfileId,username,Profile.Name from user where Username = :username];
        system.debug('..........................out of if..................................'+u.Profile.Name);
       if(u.Profile.Name == 'Investor'){
        system.debug('.........................in if.................................'+u.Profile.Name);
       invlogin();
       }
       if(u.Profile.Name == 'Advisor'){
           advlogin();
       }
        if(u.Profile.Name == 'Authenticated Website Clone'){
           AWClogin();
       }
      
   }catch(Exception e)
    {
   
    }
   }
  
      global PageReference AWClogin()  
       {
      
      
        // String startUrl = 'https://cs3.salesforce.com/secur/login_portal.jsp?orgId=00DQ0000000C4PG&portalId=060Q00000004cMI';
       
        String startUrl = ' /apex/HomePage ';
       
          system.debug('..........................username.....3..................................'+username);
           // system.debug('..........................password....3...................................'+password);
      //  system.debug('........................................3.........................'+Site.login(username, password, startUrl));
       
    return Site.login(username, password, startUrl);
      
       }
  
    global PageReference advlogin() {
   
        String startUrl = 'https://cs3.salesforce.com/secur/login_portal.jsp?orgId=00DQ0000000C4PG&portalId=060400000008v32';
          system.debug('..........................username.....1..................................'+username);
           // system.debug('..........................password....1...................................'+password);
        system.debug('........................................1.........................'+Site.login(username, password, startUrl));
       
       // site.login(username,password,'https://cs3.salesforce.com/secur/login_portal.jsp?orgId=00DQ0000000C4PG&portalId=060400000008v32');
       return Site.login(username, password, startUrl);
    }
   
    global PageReference invlogin() {
           String startUrl = 'https://cs3.salesforce.com/secur/login_portal.jsp?orgId=00DQ0000000C4PG&portalId=060400000008v37';
              system.debug('..........................username..2.....................................'+username);
            system.debug('..........................password....2...................................'+password);
          //  system.debug('......................................2...........................'+Site.login(username, password,startUrl));
           // site.login(username,password,'https://cs3.salesforce.com/secur/login_portal.jsp?orgId=00DQ0000000C4PG&portalId=060400000008v37');
           return Site.login(username, password, startUrl);   
    }   
        global kbrLogin () {
       
        getlogin();
        }
   
    global static testMethod void testSiteLoginController () {
        // Instantiate a new controller with all parameters in the page
        SiteLoginController controller = new SiteLoginController ();
        controller.username = 'nakumar@aw.com';
        controller.password = 'force123';
               
        System.assertEquals(controller.login(),null);                          
    }  
}