Hi,
I am using a custom button on lead detail page i.e. pop up and creating a pop window using javascript. That pop window has visualforce page to create new task. When i save the task it redirects me to task detail page. while i want when i click on save it redirect me to lead detail page and show the new task in open activity. please help me how do i redirect to lead detail page.

javascript code i am using on the custom button is given below:
{!REQUIRESCRIPT('/soap/ajax/26.0/connection.js')} 
{!REQUIRESCRIPT('/js/functions.js')} 
{!REQUIRESCRIPT('/resource/jQueryForPopup/jQuery/jquery-1.8.2.min.js')} 
{!REQUIRESCRIPT('/resource/jQueryForPopup/jQuery/ui/jquery-ui-1.9.1.custom.min.js')} 
{!REQUIRESCRIPT('/resource/jQueryForPopup/jQuery/postmessage/jquery.ba-postmessage.js')} 
{!REQUIRESCRIPT('/resource/jQueryForPopup/jQuery/bbq/jquery.ba-bbq.min.js')} 
requireCssFile('/resource/jQueryForPopup/jQuery/ui/css/ui-lightness/jquery-ui-1.9.1.custom.min.css'); 
function requireCssFile(filename) 
{ 
var fileref = document.createElement('link'); 
fileref.setAttribute('rel', 'stylesheet'); 
fileref.setAttribute('type', 'text/css'); 
fileref.setAttribute('href', filename); 
document.getElementsByTagName('head')[0].appendChild(fileref); 
} 

var j$ = jQuery.noConflict(); 
var iframe_url = '{!URLFOR("/apex/vfPopup")}'; 
var child_domain = iframe_url.substring(0, iframe_url.indexOf('/', 9)); 
var parent_domain = window.location.protocol + '//' + window.location.host; 
var j$modalDialog = j$('<div id="opppopup"></div>') 
.html('<iframe id="iframeContentId" src="' + iframe_url + '" frameborder="0" height="100%" width="100%" marginheight="0" marginwidth="0" scrolling="no" />') 
.dialog({ 
autoOpen: false, 
title: 'Sample Popup', 
resizable: true, 
width: 800, 
height: 540, 
autoResize: true, 
modal: true, 
draggable: true 
}); 

j$modalDialog.dialog('open');

Visualforce code is given below:

<apex:page standardController="Task" sidebar="false">
    <apex:form >
      
        <apex:pageBlock title="Edit Task" id="thePageBlock" mode="edit">
            <apex:pageMessages />
            <apex:pageBlockButtons >
                <apex:commandButton value="Save" action="{!save}" onComplete="closeModalDialog();"/>
                <apex:commandButton value="Cancel" action="{!cancel}"/>              
            </apex:pageBlockButtons>
            <apex:actionRegion >
                <apex:pageBlockSection title="Basic Information" columns="1">
                <apex:inputField value="{!Task.Ownerid}"/>
                    <apex:pageBlockSectionItem >
                        <apex:outputLabel value="Subject"/>
                            <apex:inputField value="{!Task.Subject}"/>
                    </apex:pageBlockSectionItem>
                    <apex:inputField value="{!Task.whoid}"/>
                    <apex:inputField value="{!Task.whatid}"/>
                </apex:pageBlockSection>
            </apex:actionRegion>

        </apex:pageBlock>
    
    </apex:form>
    <script type="text/javascript">
          
        function closeModalDialog() {
            var cross_result = new Object();
            cross_result.action = 'close_modal_dialog';
         
            if (cross_result.action == 'close_modal_dialog') {
            j$modalDialog.dialog('close');
            }
        } 
    </script>
    <!--<script>
        var returnURL;

        window.onload =  function(){
        returnURL = gup('retURL');
        //alert('Set retURL = ' + returnURL);
        
        };
        
        function gup( name ){  //this function just grabs HTTP params by name
        
        name = name.replace(/[\[]/,"\\\[").replace(/[\]]/,"\\\]"); 
        var regexS = "[\\?&]"+name+"=([^&#]*)"; 
        var regex = new RegExp( regexS ); 
        var results = regex.exec( window.location.href );
         if( results == null )    return ""; 
        else    return results[1];}
        
        function redirectBack(){
        //alert('Sending you back to ' + returnURL);
        window.location.href = '/' + returnURL;
        }
    </script>-->
</apex:page>