I ever recommended a CHM reader add-on for firefox2 last year which the post's title is Recommend a firefox add-on for reading CHM file , this add-on's new version 0.2.3 which supports Firefox3 is released, Following I will tell you how to get this add-on and install it.
1. Download the CHM Reader add-on from(please select the right version to your computer) :
2.Open the xml file you downloaded with Firefox 3 to install it into Firefox 3:
Once you restart the Firefox,you have intalled it successfully, you should see a Open CHM File option on File drop-down menu of the Firefox3.Now,you already can read the CHM file via Firefox 3:）