jquery dialog box
===

i'm working on a login form. 
here's the code

     <?php 
	   require_once('../../SfHelper.php'); 
	   $sfHelper = new SfHelper();
	   echo $sfHelper->load_css('ui-lightness/login');
     ?>

    
     <div name="form_Login" class="form_Login">
     <form id="form1" name="form1" method="post" action="<?php echo $sfHelper->base_url().'forms/jobseeker/'; ?>process_Login.php" >
     <table width="296" border="0" align="center" cellspacing="5">
        <tr>
           <td colspan="3">LOGIN JOB SEEKER</td>
        </tr>
        <tr>
           <td width="110">Username</td>
           <td width="18">:</td>
           <td width="209"><input type="text" name="txtUsername" id="txtUsername" /></td>
        </tr>
        <tr>
           <td>Password</td>
           <td>:</td>
           <td><input type="password" name="txtPassword" id="txtPassword" /></td>
        </tr>
        <tr>
           <td colspan="3">
	  				
	   </td>
        </tr>
        <tr>
           <td colspan="3"><div align="center">
              <input type="submit" name="Login" id="Login" value="Login" />
              </div></td>
        </tr>
     </table>
    </form>
    </div>


    <?php
	if(isset($_GET['err']))
	{
		if($_GET['err'] == "Sorry, We Cannot found your Username")
		{
			echo '<script type="text/javascript"> alert("Sorry, We Cannot found your Username"); </script>';
							
		}
	        else if($_GET['err'] == "Invalid Username or Password")
	        {
		        echo '<script type="text/javascript"> alert("Invalid Username or Password");</script>';
		}
	}
    ?>

the thing is I need to display the error message using jquery modal dialog box rather than use alert. I have no clue whatsoever about using jquery nor that i have mastered php or javascript. Can anyone show me how its done?