LOL, I wouldn't worry about that, because that's just something Windows does when you assign a
File Type to a file extension

If you click on your "
My Computer," then click on "
Tools," "
Folder Options," then select the "
File Types" tab, you will see the list of all the file types there with the associated default program that each of those file types open with. You can change them to whatever you want (as long as the file type is compatible with the program, that is

).
Again, the label doesn't alter the file in any way nor does it affect how
others view/open the file on
their computer, so if you prefer FireFox to be the default opener for "
html" file extension when clicking directly on the file on your computer, then you should leave it at that.
If however, you want to have DW be the default "
html" file opener, then you can change the program via that "
File Types" tab area I mentioned above. What this will do is whenever you open an "
html" file extension via your computer by clicking on the filename, DW will open the file for editing instead of using Firefox to just
view the file. If however, you were to open the file via Firefox, it will view as normally would through FireFox.
Another way to open the "
html" file to view it via FireFox on your computer for just a particular instance, is to
"right click" on the file and select "
Open With" then select your FireFox program (or if it's not automatically listed there, you click on "
Choose Program" and you can add the program to the list for future when "right clicking" the menu).
Knowing that you can change the "
File Types" and that you also can "right click" to open a file with another program for cases where you don't want the default program to open it, is wonderful and I use this Windows' feature all the time!