display:none not working on button click event

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server"> 

        <script type="text/javascript" >                     

      // This function handles style and display changes for each next button click

            function handleWizardNext() {

                var chkConnType;

                if (document.getElementById('ButtonNext').name == 'Step2')
                {

// Change the button name - we use this to keep track of which step to display on a click
                   // DeviceNameTextBox


                    document.getElementById('ButtonNext').name = 'Step3';

                    document.getElementById('ButtonPrevious').name = 'Step1';
        

                 // Set new step to display and turn off display of current step

                               document.getElementById('Step1').style.display = 'none';

                               document.getElementById('Step2').style.display = '';                              

                      // Change background color on header to highlight new step

                               document.getElementById('HeaderTableStep2').style.backgroundColor = '#EA8511';

                               document.getElementById('HeaderTableStep1').style.backgroundColor = '#8CC63F';

                     document.getElementById('fstep1').style.display = 'none';
                     document.getElementById('ffstep1').style.display = 'none';

                    document.getElementById('fstep2').style.display = 'block';
                    document.getElementById('ffstep2').style.display = 'block';


                           }
                        
       }
</script>

<<div  style=" position:fixed; top:150px; width:600px; height:400px;  left: 488px;">
    <div  id="fstep1" style="position:fixed; top:177px; width:538px; height:25px; background-color:khaki; left: 506px;" >     
           <td id="HeaderTableStep1" style="position:fixed; top:177px; width:500px;height:25px; background-color:khaki; left: 506px;background-color:#EA8511; color:White; font-size:larger; height:60px;">Step 1: Select Location </td>
        </div>
     <div id="ffstep1" style=" position:fixed; top:209px; width:536px; height:301px;  left: 508px;">
        </br>
        </br>
           WEL-COME TO ADD NEW WIZARD!
         </br>
        </br>
        Branch where you want to add new device  <td id="newbranch;"> &nbsp;<asp:DropDownList ID="DropDownList1"  runat="server" DataSourceID="SqlDataSource1" DataTextField="Branch_name"></asp:DropDownList></td><asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:ems_db1ConnectionString %>" SelectCommand="SELECT [Branch_name] FROM [master]"></asp:SqlDataSource>
         </br>
        </br>
      
        
            </div>


       <div id="fstep2" style="display:none; position:fixed; top:177px; width:538px; height:25px; background-color:khaki; left: 506px;" >     
           <td id="HeaderTableStep2" style="position:fixed; top:177px; width:500px;height:25px; background-color:khaki; left: 506px;background-color:#EA8511; color:White; font-size:larger; height:60px;">Step 2:Select Device Type </td>
           
        </div>
     <div id="ffstep2" style="display:none; position:fixed; top:209px; width:536px; height:301px; left: 508px;">
        </br>
        </br>
         Select Device Type: 
         </br>
        </br>
         <div style=" position:fixed; overflow:scroll;height:301px;width:536px; ">
       <asp:TreeView ID="TreeView1" runat="server"  ImageSet="BulletedList3" Width="439px" Font-Names="Times New Roman" 
                                            HoverNodeStyle-BackColor="#04B14B" HoverNodeStyle-ForeColor="White" 
                                            RootNodeStyle-ForeColor="Black" 
                                            ParentNodeStyle-ForeColor="#A92159"
                                            NodeStyle-ForeColor="Brown" 
                                            LeafNodeStyle-ForeColor="#04B14B"
                                            SelectedNodeStyle-BackColor="DeepSkyBlue" SelectedNodeStyle-ForeColor="White" Font-Size="14px" ExpandDepth="0" >
                                            </asp:TreeView>  

             </div>
        
    </div>
        <input id="ButtonNext" type="button" style="height:40px; width:80px" value="Next" name="Step2" onclick="handleWizardNext()" />
      </div>