App_offline.htm, CSS, images, and aspnet_isapi.dll

Question

So, the site I'm working on is using urlrewriting in coordination with aspnet_isapi.dll (everything is mapped to it). I put up my app_offline.htm file, and all the text shows, however, the CSS or images aren't being served. I'm guessing they're being processed by ASP.NET due to the wildcard mapping instead of IIS. Is this correct? If so, how can I allow IIS to serve these files? Furthermore, an issue I can see arising..in the web.config for the rewriter settings:

<rewrite url="^~/images/network/(.*)/(.*).jpg$" to="~/services/ImageHandler.ashx?type=$1&amp;id=$2"/>
    <rewrite url="^~/image/view/(.*).jpg$" to="~/ServePRView.aspx?id=$1"/>
    <rewrite url="^~/asset/view/(.*).jpg$" to="~/services/ImageHandler.ashx?id=$1&amp;type=asset"/>

Thanks for the help all, -Steve

Answer 1

It's because if the webserver sees an App_Offline.htm file, it serves that file for every request in the site - even images. You have to serve images from another site. Or you can try something like this http://en.wikipedia.org/wiki/Data_URI_scheme

Answer 2

@JeremyWeir is correct. IIS stops serving sub resources in the prescense of app_offline.htm A way around this is to embed the content in the page directly by using:

1) Encode Images inside Html 2) Internal Style Sheets 3) the same for your javascript

This isn't the easiest to maintain but it does give you control over the appearance of the content displayed on the page.