At Muti-sites System,
when loading a image witch in a page of the site,
at first time, it's will be fine.
bug if refresh the page by Command+R, it's will not appear.
the I checked the wp-includes/ms-files.php found that when the second time to access the image with HTTP HEADER HTTP_IF_NONE_MATCH and HTTP_IF_MODIFIED_SINCE, it's will be response 304 AND with Content-Length > 0, but there isn't any content be response, then safari be crying...
Finally, I was add below line to ms-file.php
header( 'Content-Length: 0' );
It's fine now.