RTasks.net is a website application, which means it is accessed through a Web Browser. The web browser you use (Google, Firefox, etc...) may offer to "Save your password?" as the user is logging in. If you press "Yes", any user can log into RTasks under your credentials. It is very important that you do not save your RTasks password on a device that other people are using.
If you save your credentials, this document outlines how to delete saved passwords (from all websites) Google Chrome, Internet Explorer, and Fire Fox browsers.