Hello,
i have the JavaScript function named 

function open_win_URL(pagename) {

But when i download this using HTTrachk tool, the 
downloaded page has been wriiten like this

function open_win_URL(pagename.html) {

The .html extension is get attached automatically since the 
function name contains URL. As a effect of this, the 
downloaded page throws JavaScript error.

Is it a bug? or is there any workaround for this.

Any function whose name contains "URL" as a string, that 
functions parametres gets an .html extension.