Why is the filesize of downloaded disk image different? I have a disk image which I uploaded to a web server and then downloaded with Safari 5.1 in OS X 10.7.

Finder reports the original as 34,911,334 bytes, and the downloaded file as 34,909,684. Both appear to contain identical contents when mounted.

What's going on here?

Edit: See output of ls -l@ and md5 as suggested:

$ ls -l@
total 136376
-rw-r--r--@ 1 rich  staff  34909684 15 Aug 16:37 Downloaded.dmg
    com.apple.diskimages.fsck         20
    com.apple.diskimages.recentcksum          80
    com.apple.metadata:kMDItemDownloadedDate          53
    com.apple.metadata:kMDItemWhereFroms         144
    com.apple.quarantine          74
-rw-r--r--@ 1 rich  admin  34909684 15 Aug 12:42 Original.dmg
    com.apple.FinderInfo          32
    com.apple.ResourceFork      1650
    com.apple.diskimages.recentcksum          80

$ md5 Original.dmg
MD5 (Original.dmg) = 4c1ed7a85de6ae51479a136ea23ac69e

$ md5 Downloaded.dmg
MD5 (Downloaded.dmg) = 4c1ed7a85de6ae51479a136ea23ac69e
The difference of 1650 bytes is probably the result of the resource fork being stripped from the uploaded disk image.

To test, I created a disk image from a folder in Disk Utility. I then used 

ls -l@


in the folder that contained the disk image, and it showed the image had a resource fork that was 1650 bytes.