Hopefully this helps if you’re experiencing any difficulties with your auto-configuration scripts.
![internet explorer cannot download aspx file internet explorer cannot download aspx file](http://www.techsupportall.com/wp-content/uploads/2013/05/This-file-contained-a-virus-and-was-deleted1.png)
I seemed to have strange behaviour when using https to access the proxy pac file – some sites would simply fail to load. Lastly, I decided to switch the proxy pac file URL from a https secure URL to plain http. Shame, as that was a very useful way of seeing what was happening during processing. I also found that using the alert() function in the proxy pac file appeared to be ignored. Not ideal during normal circumstances, but handy when you’re making changes to the proxy pac file. After that, the pac file was used for every request. I applied the registry setting and restarted Internet Explorer. New DWORD (32 bit) EnableAutoproxyResultCache HKEY_CURRENT_USER\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings For testing, I was able to change this behaviour with a registry setting, disabling the caching of proxy servers. This is where I learnt that Internet Explorer 11 by default would remember which proxy server it had used to access a web site, and then continue to use that same proxy server. Therefore any changes I made to the proxy pac file seemed to be irrelevant to sites I had already accessed. For interest, I was using Wireshark to check network traffic to the proxy pac web server. I started seeing intermittent results where the pac file would sometimes be downloaded, and sometimes not. I disabled the Automatically detect settings option and enabled the Use automatic configuration script option, supplying the URL of the proxy pac file that I created (e.g. With that in place, I configured the Internet Explorer 11 proxy settings. If one of these sites is the target then use the proxy, otherwise connect directly. I’m simply checking for any request with a host that ends in or. The format of the proxy pac file is fairly straight forward. Var strProxy = "PROXY proxy-server-host-name:8080"
![internet explorer cannot download aspx file internet explorer cannot download aspx file](https://i.stack.imgur.com/sDVgG.png)
With that in place, I was then able to create and upload a sample proxy pac file. don’t use something else like application/octet-stream). The MIME type application/x-ns-proxy-autoconfig appears to be a requirement (i.e. I created a folder on the web site to host the proxy pac file, and then included a web.config file with the contents below. By default, IIS does not serve pages for which it does not have a registered MIME type. You can fix this with the IIS Management Console, or by using a web.config file (which is what the Management Console does anyway). Given that local proxy pac files can no longer be used, I copied the pac file to a web server that I have (running IIS 8.5).
![internet explorer cannot download aspx file internet explorer cannot download aspx file](https://media.itpro.co.uk/image/upload/s--X-WVjvBW--/f_auto,t_content-image-full-desktop@1/v1601052292/itpro/Web_Browser_Shutterstock.jpg)
Internet Explorer 11 will by default remember (cache) which proxy server to use for each web site, making any pac file changes difficult to test.Internet Explorer 11 does not seem to honour the alert() function call in the pac file, making troubleshooting a little more complex.
![internet explorer cannot download aspx file internet explorer cannot download aspx file](https://images.drivereasy.com/wp-content/uploads/2020/01/2020-01-02_11-39-45.jpg)