|Project:||Responsive images and styles|
Since I updated to Drupal 7.20, some responsive images of my website are not visible. That is the case for the images uploaded/created after the core update. (Images not controlled by this module are fine.)
Cf. the update notes of the current core release about an important change in image generation: drupal-7.20-release-notes:
... any code which programmatically generates a link to an image derivative without using the standard image_style_url() API function will no longer work correctly if the image does not already exist in the file system ...