I don't think the problem is in your URL definition. After I checked the url you said, it in fact has a customized page for the HTTP Error 404, which means resource not found. However, the url
http://www.merchant.com/index.html is valid and should give you the expected result.
[Explanation]
What it means is; You are trying to retrieve content from a file that does not exist in the destination URL. In order to read the URL successfully, you must first create a file in the directory named pg of your hosting server. Then in this server, copy your file or create a file that you want to be accessible. Otherwise, you will have to use a valid location to retrieve the file content.
N.B. If you the url does not point to an existing file, you will get a file not found exception...which I suppose is what you're getting in your stack trace.