2 solutions:
-You put your adsense code where you want to see ads... duh

in this
case in the search results page (depending on which search technology
you are using, this could be in a template provided by your search)
-If you look at the html code of simplyhired, it doesn't look like your
regular copy-paste Adsense code, so most likely they have made special
arrangements with Adsense.