If you right-click the link and click "save as" then select it wherever you downloaded it, click open with and select firefox. there should be a checkbox saying "Remember application association for all files of type "HTML document" (text/html)"

I'm not sure if this will work in the way you need, but it worked for me

If you right-click the link and click "save as" then select it wherever you downloaded it, click "open with" and select firefox. there should be a checkbox saying "Remember application association for all files of type "HTML document" (text/html)"

I'm not sure if this will work in the way you need, but it worked for me