Your browser consults two files in your home directory for interpreting and handling documents with unusual filename extensions.
.mailcap .mime.typesIt is assumed that you have the hamlet application installed on your system in one of the standard system paths. Then to process documents with the .hamlet extension, the .mailcap file should have the following entry:
text/x-hamlet-action; hamlet %sand the .mime.types file should have
type=text/x-hamlet-action exts=hamletIf these entries are not present in those files, you should add them and restart the browser.