jquery error:microsoft jscript runtime error '$' is undefined jquery?
===

i used the following jquery for validation of particular div.
    <script type="text/javascript">
    $('#btnNext').Click(function()
    {
    if ($('#page1 input[id$=txt_companyname]').val() == "")
    {
    alert('company Name is Blank!');
    $('#page1 input[id$=txt_companyname]').focus();
    }
    else if ($('#page1 input[id$=txt_headoff]').val() == "")
    {
    alert('Password is Blank!');
    $('#page1 input[id$=txt_headoff]').focus();
    }
    });
    </script>