Well, I downloaded your file from the specified link you have refered. The file is not a native excel file so, you are getting the error by Aspose.Cells, it's rather a web page / .html file. For cofirmation, you may open it into the notepad and check it. To make the file as a native excel file, kindly open it into MS Excel (e.g.., 2000-2003), now save it as "Microsoft Office Excel Workbook". Now you may use Aspose.Cells APIs to work with the file.