Why I can not find some css with grep?
Please check Remove width and height from img tag in Drupal output (for certain content type) for removing width and height from image.

You will never find width and height with grep command because width and height are added by drupal theme function.

Check https://api.drupal.org/api/drupal/modules%21image%21image.module/function/theme_image_style/7 and  https://api.drupal.org/api/drupal/includes%21theme.inc/function/theme_image/7 for more details.