title: XAP Expires after half a Day?
body: <p>Im just wondering what would be causing my xap to expire every half day (approx). What i mean is that in the morning a user hits the website and it downloads a copy of the xap, by the afternoon if that user goes back to the website and the website downloads another copy of the xap for them.</p>
  
  <p>I would hope that the only reason that a user should need to download a new copy of the xap would be when they have cleared their browser cache or ive put a new copy up on the server.</p>
  
  <p>Any ideas on what would be the problem and fix?</p>
  
  <p>I ran fiddler on the XAP download and got the following lines from the cache tab of the xap download entry in fiddler. </p>
  
  <p>HTTP/200 responses are cacheable by default, unless Expires, Pragma, or Cache-Control headers are present and forbid caching.</p>
  
  <hr>
  
  <p>HTTP/1.1 ETAG Header is present: "2ad1d6bfdd43cb1:0"
  HTTP Last-Modified Header is present: Tue, 24 Aug 2010 22:43:19 GMT</p>
  
  <p>No Explicit HTTP Expiration information was provided. Most browsers utilize heuristic expiration policies:
  10% of the delta between Last-Modified and Date is '02:53:34' so this response will heuristically expire 26/08/2010 4:39:26 PM.</p>
  
  <hr>
  
  <p>Would this be what the problem is? Where do I set explicit HTTP expiration?</p>