How do I POST to a web page using Firebug?
You can send POST request to any page by opening console (e.g. in FireFox ctrl + shift + k) and typing simple JS:
var formPost = document.createElement('form');
formPost.method = 'POST';
formPost.action = 'https://www.google.com'; //or any location you want
document.body.appendChild(formPost);
formPost.submit();