title_body: Stretching an image to fit the screen
upvoted_answer: unfortunately you can't make width:100%; in mobi files. Amazon just strip that away. You can try to set min-width:100%; instead but this is little different in behave so test are needed. More about which CSS kindle respect you can read in this documentation. 
  
  2017/06/27
  Changes in KF8 format allow now using width css property