Simple Desktop Browser OR CHROME EXTENSION to log in into a website

Hello so i have a website THAT I DON'T OWN! i need to do a simple chrome extension or a simple browser, so whenever the user activate it it will send him to a website already logged in, AGAIN I DON'T OWN THAT WEBSITE.

For example I activate the extension and it will send me to Facebook.com with an account already logged in, THIS IS AN EXAMPLE!