this will send a form with preloader :
var a=$('#yourform').serialize();
$.ajax({
type:'post',
url:'receiver url',
data:a,
beforeSend:function(){
launchpreloader();
},
complete:function(){
stopPreloader();
},
success:function(result){
alert(result);
}
});
i'have some trick to make a form data post reformed with random method http://www.jackart4.com/article.html