I honestly cannot tell you the number of times that I have had to clear all of my browsing history while developing websites and dealing with logins. Sessions, Cache, Cookies, Temporary Files, and History all play a part in how and when your browser asks the server for information, compared to when it can find the information it is looking for, locally. After a number of years, it seems that all of today’s browsers (Firefox, Chrome, and Internet Explorer) have finally realized the same [Control] + [Shift] + [Delete] command.
To quickly reach your “Clear Everything” options, in Firefix, Chrome, and Internet Explorer, simply press and hold [Control] + [Shift] + [Delete] while a browser window is open. You will then have the option to quickly clear all of your temp settings and move on to testing your website. Just a quick hint.