There is nothing to download for the browser except a standard web page.
If you use Windows XP SP2 you might get a warning “…restricted this file from showing active content…” The warning only appears during testing and not when the web page is published to a web server.
Please upgrade to version 3.1.9 or later.
SpreadsheetConverter for HTML version 2 support NS4 and IE4 and later.
SpreadsheetConverter for HTML version 3 requires NS7 and IE5 and later.
NS4 and IE4 is virtually non-existent nowadays.
Use Opera instead. The SpreadsheetConverter pages work fine using Opera as the browser.