title: How to make an iAd integrated iPhone app working on previous versions of iPhone OS?
body: <p>As title described, I integrated iAd into my iPhone apps. Everything worked fine in the iPhone simulator (iOS4). However, when I try to install it on my iPhone(version 3.1.3), I got an error:</p>
  
  <pre><code>  dyld: Library not loaded: /System/Library/Frameworks/iAd.framework/iAd
    Referenced from: /var/mobile/Applications/...
    Reason: image not found
  </code></pre>
  
  <p>I already properly set the deployment target to v3.0, and base SDK to 4.0. When I comment out all the iAd related code, the apps installs with no problem. </p>
  
  <p>There must be a way to do this, because I downloaded the apps "showtimes" and "Yellow Pages", which use iAd. Both apps run very well on my 3.1.3 phone, and I can see the iAd as well. </p>
  
  <p>Does anybody know how to do this?</p>