Change drupal standard messages like "You have just used your one time login link" I'm having trouble with changing drupal default messages. 

Like for example when you register you get an email with a one time login link (I know how to change this email text) and when you click on the link you get the message


  This is a one-time login for username and will expire on ... .
  
  Click on this button to log in to the site and change your password.
  
  This login can be used only once.


But how can I change this text? Another example is:


  You have just used your one-time login link. It is no longer necessary to use this link to log in. Please change your password.


How can I change these texts?
Try the String Overrides module. If you have more strings to change.

Provides a quick and easy way to replace any text on the site.
Features

Easily replace anything that's passed through t()
Locale support, allowing you to override strings in any language
Ability to import/export *.po files, for easy migration from the
Locale module
Note that this is not a replacement to Locale as having thousands of
overrides can cause more pain then benefit. Use this only if you need
a few easy text changes.