$.ajax({
type: "POST",
url: this.url,
data: form_data,
beforeSend: function() {
$('#ajaxDetails').addClass('progress');
},
error: function() {
$('#status').text('Update failed—try again.').slideDown('slow');
},
success: function() {
$('#status').text('Update successful!');
},
complete: function() {
$('#ajaxDetails').removeClass('progress');
setTimeout(function() {
$('#status').slideUp('slow');
}, 3000);
}
});

var form_data = $("form").serialize();
var form_data_array = $("form").serializeArray();

$(document).ready(function() {
$('#submit').click(function () {
var name = $('.uname').val();
var data = 'uname=' + name;
$.ajax({
type:"GET",
url:"welcome.php",
data: data,
success: function (html) {
$('#message').html(html);
}
});
return false;
});
});


and MVC3 Ajax

@using (Ajax.BeginForm(       
  "ActionName",          
"ControllerName",         
 new AjaxOptions {
 UpdateTargetId = "modal-dialog",  
 OnFailure="searchFailed",            
OnBegin = "Dialog.Updating()",             
 OnSuccess = "Dialog.Update({title:'Select Friends'})"        
 })) { 
        …           <input type="submit" value="Next" /> 
}