How can I avoid Yahoo search and link click from getting "octet stream" prompt in Gecko-based browser?

Doing any search from Yahoo home page brings up results. Clicking on any of the search results results in my gecko-based browser (i.e., Firefox, SeaMonkey, Camino, K-Melon) cause a pop-up asking how to open an "octet stream" instead of immediately directing me to the website. Why?