<p>If you add a image to your browser's DOM, IE6 will not check its cache to see if it already downloaded the image but will, instead, re-retrieve it from the server.  I have not found any combination of HTTP response headers (of the ensuing image request) to convince IE6 that it can cache the image:  Cache-control, Expires, Last-modified.</p>

<p>Some suggest you can return a 304 of the subsequent image requests to tell IE6 "you already got it" but I want to avoid the whole round trip to the server in the first place.</p>

[{'answer_id': 62836, 'author': 'dwilkins', 'author_id': 6728, 'author_profile': 'https://Stackoverflow.com/users/6728', 'pm_score': 0, 'selected': False, 'text': '<p>A quick google mentions the "Expires" header, which you\'ve already tried.  Digging deeper, it mentions the ETag header:</p>\n\n<p><a href="http://mir.aculo.us/2005/08/28/internet-explorer-and-ajax-image-caching-woes" rel="nofollow noreferrer">http://mir.aculo.us/2005/08/28/internet-explorer-and-ajax-image-caching-woes</a></p>\n\n<p>Hope this helps.  </p>\n'}, {'answer_id': 209653, 'author': 'Ionuț Staicu', 'author_id': 23810, 'author_profile': 'https://Stackoverflow.com/users/23810', 'pm_score': 1, 'selected': False, 'text': '<p>Maybe <a href="http://www.mister-pixel.com/index.php?Content__state=is_that_simple" rel="nofollow noreferrer">this</a> will work? (is the same behaviour like hovering on links with css background image)</p>\n'}]
['https://Stackoverflow.com/questions/62530', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/6942/']