As a note, writing your passwords on a sticky note is just as dangerous!
To Forget PasswordsTo protect yourself, here is how to get rid of all your saved passwords:
Click on Chrome -> Clear Browsing Data...:
Then click on Clear Browsing Data.
Click on Safari -> Preferences...:
When the window pops up, click on Passwords at the top:
Click on Remove All to delete every saved password in Safari.
Click on Firefox -> Preferences...:
In the window that pops up, click on Security and UNCHECK Remember passwords for sites:
Then click on Saved Passwords...:
Click on Remove All to clear all saved passwords from Firefox.
Next time the browser offers to save your passwords, please just say no.