The iMac Mid-2010 supports DDR3 10666 (from the Apple support site)
The first link is to the correct RAM for that Front Side Bus (FSB) speed
The second link is to a slightly quicker set of RAM, but runs on a lower FSB.
The differences between the two are characterised by the two notes above, the FSB speed and the clock timings.
In the first, the FSB speed is higher, but the timings for the RAM are slower. In the second, the slower FSB allows the RAM to work at slightly faster timings.
If you want to know about timings, a search for RAS CAS delay is a good starting point.
Apple's memory upgrade page for your model iMac calls for PC-10600 SO-DIMMs.
http://support.apple.com/kb/ht4255
Those Corsair SO-DIMMs meet all the stated specifications, even though some sites erroneously list them as PC-10666 (Corsair lists them as PC-10600).
Furthermore, if you look through the reviews on Newegg and other sites for this memory, you can see reports of people using it successfully in their Macs.
So I would conclude that yes, it's safe to use it in your 2010 iMac.
Best Answer
From iMac (Mid 2010: Memory specifications):
And from iMac: How to remove or install memory: