<a href='#' id='TakeView'>Снять показ</a>
........
<script>  
         $(document).ready(function(){ 
		           
             $('#TakeView').click(function(){  
                 $.ajax({  
		     type: 'GET',
                     url: 'takeview.php',  
		     data: 'firmid=".$tfid."',
                     success: function(msg){  
                         alert('Снят показ!'+msg);  
                     }  
                 });  
             });  
        });  
     </script>  

<?php

  include "serverconnect.php";
  include "globalfunctions.php";
    
  
  $sql = "SET NAMES utf8";
  mysql_query($sql, $conn);


	$fid = $_GET['firmid'];
	
	$sql = "SELECT viewsleft FROM tblh4329hh3_firm Where Id = '$fid'";
	$result = mysql_query($sql, $conn);
	if(mysql_num_rows($result))
  	{
		$record = mysql_fetch_array($result);
		$viewsleft = $record[ 0 ];
	}

	$viewsleft--;

	$sql = "UPDATE tblh4329hh3_firm SET viewsleft = '$viewsleft' Where Id = '$fid'";
	mysql_query($sql, $conn);
	
	echo "12345";
?>

UPDATE tblh4329hh3_firm 
SET viewsleft = viewsleft -  1 
Where Id = '$fid'