I was looking for the Wahu Mega Pool Pack on google then I clicked the link off the google sponsored shopping section for oo.com.au. Once I got to the page, I looked at other items and this image popped up underneath the product menu saying:
$10 OFF SITE WIDE * Expires in:** Just for you. Coupon will be automatically applied to your cart. * when you spend over $75 on product, excluding delivery charges
When my sister looked at the same site, she could not see this $10 off site wide, so I went to oo.com.au in a different browser but it didn't show up either. It looks like you need to click off the google link, then go to another page within the site before you see the message (worked for her, worked for me on different browser).
If in doubt, google Wahu Mega Pool Pack and go to the right hand sponsored shopping links and click the oo.com.au one and it should work.
Expires 11am 23/11/2013.
Got it to work via the method you described above.
The coupon seems to expire 12 hours after you visit the site so doesn't expire at 11am like you stated :)