mysql_fetch_array() error

hi guys,  i can't resolve this error "The requested URL /<br /><b>Warning</b>: mysql_fetch_array() expects parameter 1 to be resource, boolean given in <b>/home/nerdto/greenfair/include/bit_functions.inc.php</b> on line <b>33</b><br />//auction/ was not found on this server."

where is the problem?

thanks

function getStart($limit)

{

if((!isset($_GET['page'])) || ($_GET['page'] == "1")) {

        $start = 0;

        $_GET['page'] = 1;

     } else {

        $start = ($_GET['page']-1) * $limit;

     }

     return $start;

}

function get_cat_name($cat)

{

$rec=mysql_fetch_array(mysql_query("select name,top from add_category where id=$cat"));

 

 if($rec['top'] > 0)

 {

return get_cat_name($rec['top'])."/".str_replace(" ","-",trim($rec['name']));

 }

 else

 return str_replace(" ","-",trim($rec['name']));

 

}