I don't know if konqueror or mozilla have plugins to CHM files, but there are in linux severals applications:
CHM Decompressor: archmage.
About MHT, in the wiki it says:
"As of version 3.5.7 (released 2007-05-02), KDE's Konqueror web browser does not support MHTML files. However, it does include a feature for saving web pages as single files ("web archives", file extension .war) which are actually gzipped tarballs. (but there is a side project mhtconv that allows to use MHTML with Konqueror for both 3.x and 4.x KDE branches)"
Moreover, kmhtConvert perhaps can help you.
P.D: I don't talk english very well... sorry.