The MIME Type reply is generally set correctly so browsers are able to pass the reply to the correct module (image, text, html, flash, music, mpeg, etc.)
One popular example is to block flash video, used by sites such as Youtube.
The MIME type for such content is "video/x-flv". Creating an ACL to block this is easy.
First, create an ACL which matches the MIME type in question:
acl deny_rep_mime_flashvideo rep_mime_type video/x-flvThen create a HTTP Reply ACL which denies any replies with that MIME type:
http_reply_access deny deny_rep_mime_flashvideoThis has been verified to block Youtube flash video content.
If the content is blocked the following similar line will be seen in access.log:
1282485682.146 903 127.0.0.1 TCP_DENIED_REPLY/403 3143 GET http://tc.v15.cache3.c.youtube.com/videoplayback? - DIRECT/220.127.116.11 text/html
And on browser, you can see ...