Thank you for your query.
I tried to open your sample Web GUI in different browsers (Safari, Chrome, Firefox and IE Explorer) but could not open it here.
Please note that Aspose.Html can create HTML using URL as shown in the following working example:
using (var document = new Aspose.Html.HTMLDocument(@"https://httpbin.org/forms/post"))
You may please try the above sample code as it is to see the output and try with your own sample WEB GUI as well. If you face some issue please write back to us along with the details and working code sample for our reference.