Message box(java script)

\\msgbox
if ($txtLname=='')
{
    echo'<script type="text/javascript">';
    echo'alert("Error: Last Name empty, Please fill up.")';
    echo '</script>';
}

\\clear\focus

function exist()
{
    alert("Company Description already exist");
    document.form1.txtCName.value='';
        document.form1.txtCName.focus();
}