Sure. 

Since I am just getting started with creating the page, I initially tried the sample code that was included upon creating my force.com account (in other words, the VF and controller code that was provided by salesforce.com).

I simply copied the VF code into a different page...and added the reference to the "SiteLoginController".  That is all I did.

I question whether the problem is the code itself.  I did not know if the sandbox is triggering the standard force.com login page to initially appear...or if there was some other command I should use to let the system know that this was an authentic login page.

I appreciate the help.

<apex:page controller="SiteLoginController" id="loginPage" showHeader="false" title="{!$Label.site.site_login}">
  <apex:composition template="{!$Site.Template}">
    <apex:define name="body">  
      <center>
        <apex:panelGrid bgcolor="white" columns="1" style="align: center;"> 
          <br/>
          <br/>
          <apex:panelGrid width="758" cellpadding="0" cellspacing="0" bgcolor="white" columns="1" style="text-align:left; border:1px solid #ccc;"> 
            <br/>
            <apex:outputPanel layout="block" style="background-color: white; border: 1px solid #ccc; padding: 0px; margin-top: 10px; margin-bottom: 0px; margin-left: 10px; margin-right: 10px;">
              <apex:panelGrid width="758" cellpadding="0" cellspacing="0" bgcolor="white" columns="2"> 
                <apex:image url="{!$Site.Prefix}{!$Label.site.img_path}/clock.png"/>
                <apex:panelGroup >
                  <br/>
                  <apex:outputText style="font-size: larger; font-weight: bold;" value="{!$Label.site.login}"/>
                  <br/>
                  <c:SiteLogin id="siteLogin"/>
                  <br/>
                </apex:panelGroup>
              </apex:panelGrid> 
             </apex:outputPanel>
            <c:SiteFooter />
          </apex:panelGrid> 
       </apex:panelGrid>
      </center>
      <br/>
    </apex:define>
  </apex:composition>
</apex:page>


************************************

CONTROLLER

/**
 * An apex page controller that exposes the site login functionality
 */
public class SiteLoginController {
    public String username {get; set;}
    public String password {get; set;}

    public PageReference login() {
        String startUrl = System.currentPageReference().getParameters().get('startURL');
        return Site.login(username, password, startUrl);
    }
    
    public SiteLoginController () {}
    
    public static testMethod void testSiteLoginController () {
        // Instantiate a new controller with all parameters in the page
        SiteLoginController controller = new SiteLoginController ();
        controller.username = 'test@salesforce.com';
        controller.password = '123456'; 
                
        System.assertEquals(controller.login(),null);                           
    }    
}