Thank you so much for ur response,

I am able to open a child window and close it.Actually i am trying to do the lookups as in salesforce using visual force. i was dispalyed the values as picklist in child window.but i was unable to pass the child window picklist value into parent window text filed.plz guide me.

My code is as follows:

VF 1:

<apex:page standardController="CAF_Charge__c" extensions="g_popupwindow">
<h1> CAF Charge Detail </h1>
<apex:form >
<table>
 <tr>
  <td>
    <apex:outputText value="Charges Head"/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    <apex:inputText value="{!parentTextId}"/>
    <input type="button" onclick="openPopup()" value="search" />

  </td>
 </tr>
 <tr>
  <td>
    <apex:outputText value="Description Of Charges"/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    <apex:inputtext value="{!doc}"/>
  </td>
 </tr>
 <tr>
  <td>
    <apex:outputText value="Percentage"/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    <apex:inputtext value="{!percentage}"/>  
  </td>
 </tr>
<tr>
   <td>
    <apex:commandButton action="{!save}" value="Save"  />
    <apex:commandButton value="New"  />
   </td>
</tr> 
</table>

<script>
var newWin=null;
 function openPopup()
 {
    var url="/apex/ge2";
    newWin=window.open(url, 'Popup','height=500,width=400,left=100,top=100,resizable=no,scrollbars=yes,toolbar=no,status=no');
    newWin.focus();
    
    return false;
 }
 function closePopup()
  {
    if (null!=newWin)
    {
      newWin.close();
    } 
  }
</script>

</apex:form>
</apex:page>

VF 2:

<apex:page standardController="CAF_Charge__c" extensions="g_popupwindow">
<apex:form >
<apex:pageblock >
<apex:pageBlockSection >
      <apex:pageblocksectionItem >
          <apex:outputlabel value="Charges Head" for="SelectedFromPickList" />     
          <apex:selectList value="{!selectedRecordId}" size="0" id="SelectedFromPickList">
          <apex:actionSupport event="onchange" reRender="Course" action="{!something}"/>        
          <apex:selectOptions value="{!ChargeNames}"/>
          </apex:selectList>
      </apex:pageblocksectionItem> 
      <input type="button" onclick="CloseWindow()" value="OK" />
   <!--   <apex:pageBlockSectionItem >
     
          <apex:selectRadio value="{!selectedRecordId1}" id="Course" layout="pageDirection" >
               <apex:selectOptions value="{!Charge_Field}"/>
                <apex:actionSupport event="onchange" action="{!nothing}" status="status" reRender="btnsave,btncncel"/>
             </apex:selectRadio>
       
      </apex:pageblocksectionItem>-->  
                                      
                              
  </apex:pageblocksection>
 </apex:pageblock>
 
 <script language="javascript" type="text/javascript">
   function CloseWindow()
    {
      var winMain=window.opener;
      if (null==winMain)
      {
         winMain=window.parent.opener;
      }
      winMain.closePopup();
   }
    
  </script>  
</apex:form>
</apex:page>

Controller:

public class g_popupwindow
{

    public g_popupwindow(ApexPages.StandardController controller) {
    }
      public string parentText;
      public string selectedRecord;
      public string selectedCharge;
      public string SelectedFromPickList;
      Public string chargeshead{get;set;}
      Public string doc{get;set;}
      Public string percentage{get;set;}
      public string chead;      
        
    public string getselectedRecordId()
    {
        return selectedRecord;
    }
    public void setselectedRecordId(string s)
    {     
        this.selectedRecord=s;
    }
    public string getselectedRecordId1()
    {
        return selectedCharge;
    }
    public void setselectedRecordId1(string s)
    {     
        this.selectedCharge=s;
    }
  
   
    public void something()
    {
    setselectedRecordId1(selectedRecord);
    }
    public void nothing()
    {
    }
    //....! Dispalying charge values as picklist
    public List<SelectOption> getChargeNames()
    {
      List<SelectOption> options = new List<SelectOption>();
      List<chiranjeevi__CAF_Charge__c> chargelist= new List<chiranjeevi__CAF_Charge__c>();
      chargelist = [Select chiranjeevi__Charges_Head__c FROM chiranjeevi__CAF_Charge__c ];
      options.add(new SelectOption('--None--','--None--'));
    
      for (Integer j=0;j<chargelist.size();j++)
      {
       options.add(new SelectOption(chargelist[j].chiranjeevi__Charges_Head__c,chargelist   [j].chiranjeevi__Charges_Head__c));
      }
      return options;
    }
   
    //....! storing selected charge from picklist to radio buton here
   
     public list<selectoption> getCharge_Field() 
   
    {
   List<SelectOption> SelectedFromPickList = new List<SelectOption>();
    
      if(selectedRecord == NULL)      
      {
        SelectedFromPickList.add(new selectoption('','NONE'));
      }  
       
      else
      {
         SelectedFromPickList.add(new selectoption('',' '+selectedRecord));
        }
         return SelectedFromPickList;
    }  
}

Thanks in advance,

Manu..