title: IIS 7.5 Custom 503 error page
body: <p>I have a site using asp.net and WebAPI deployed on IIS 7.5. Normal site usage is steady but occasionally there are bursty spikes with very high usage and users get very slow response timeouts. There is no option to improve performance at this time and the client has asked for a quick fix involving a customised 503 error page with the same look as the rest of the site. </p>
  
  <p>The single IIS server sits behind a load balancer and there is the option of adding a 2nd server purely to serve a static error page when the site is under heavy load. There has been a suggestion of a solution where slow responses trigger all subsequent requests go to the static server and get the custom 503 error page until the usage subsides.</p>
  
  <p>As far as I can see its not possible to customise the default 503 error page that is served automatically by IIS when its request queue is full. </p>
  
  <p>I can't see anything on SO about how to solve this sort of issue - can anyone help? </p>