From what it looks like, your attributes are incorrectly formatted. Usually it's something like : http://www.example.com?variable_name=value&variable_second=value_second . I don't see any variable names in your url, just values -so something's up with that.
Edit: Okay, I got it working on my machine and yes, your attributes are missing an "=" sign. I opened up the readme and the direction state:
*Test that the proxy is able to forward requests directly in the browser using:
http://[yourmachine]/DotNet/proxy.ashx?http://services.arcgisonline.com/ArcGIS/rest/services/?f=pjson
* Edit the proxy.config file in a text editor to set up your proxy configuration settings. * Update your application to use the proxy for the specified services. In this JavaScript example requests to route.arcgis.com will utilize the proxy.
Because I put the files in the root directory for a test (and not in the DotNet folder) , I shortened the url. the working URL for me was:
http://localhost:64875/proxy.ashx?http://services.arcgisonline.com/ArcGIS/rest/services/?f=pjson
^^ note the ending has an "=" sign. depending on where your proxy.ashx file is you might need to use a different location.