Open Modal Popup window not working

Hi .

I am trying to make items opened in a Modal popup window, in the home page of a site.
I am using the following function:

<script language="javascript" type="text/javascript">
function OpenDialogUsing_showModalDialog() 
{         
	var dialogOptions = SP.UI.$create_DialogOptions();         
	dialogOptions.url = 'LinktotheItem';         
	dialogOptions.width = 650;         
	dialogOptions.height = 300;    
                allowMaximize= true; 
                showMaximized= false;
	SP.UI.ModalDialog.showModalDialog(dialogOptions);         
	return false;     
}</script><a onclick="javascript:OpenDialogUsing_showModalDialog(); return false;" href="#">Test</a>