If you forgot your password, you can easily reset it using the forgot password link on the login page. All you need is your username.

When you log in to Salesforce from a browser or application that we don’t recognize, and your IP address is outside a trusted IP range, you’re prompted to verify your identity.

1. On the login page, click the forgot password link.
2. Enter your username and click Continue. An email containing instructions to reset your password is sent to the address specified in your Salesforce personal settings.
3. Within 24 hours, click the link provided in the email, answer your security question, and click Continue. (The link in the email can be used only once, and expires after 24 hours.)
4. When prompted, enter a new password.