Flash message _fid parameter remove.

fid-remove.js

(function (w) {
	'use strict';
	const TIMEOUT = 2000;
	const FID_QSA = '_fid=';
	function removeFid() {
		var url = w.location.search.toString();
		var fidPosition = url.indexOf(FID_QSA);
		if (w.history && w.history.replaceState && fidPosition !== -1) {
			var repairedUrl = url.substr(0, fidPosition) + url.substr(fidPosition + 10);
			while ((repairedUrl.substr(repairedUrl.length-1) === '?') || (repairedUrl.substr(repairedUrl.length-1) === '&')) {
				repairedUrl = repairedUrl.substr(0, repairedUrl.length-1);
			}
			w.history.replaceState({}, null, w.location.pathname.toString() + repairedUrl + w.location.hash);
		}
		return true;
	}
	w.addEventListener('beforeunload', removeFid);
	setTimeout(removeFid, TIMEOUT);
}(window));