Short answer - frames & security updates in Chrome.
See Peter Grainge's site (grainge.org) and search for the snippet on Chrome.
Good news is that it's fixed in RH10 with HTML5 coding.
Message was edited by: Jeff_Coatsworth: typos
Methinks you are awfully confused. "Microsoft HTML Help *IS* CHM format!
I'm guessing here that you are referring to WebHelp?
And yes, X5 is pretty old. It had no clue about anything Google Chrome related.
Helpful and Handy Links
As Rick mentioned Microsoft HTML help(CHM) has it's own viewer and if you try to open that in any browser it will give you a prompt to save the file however it won't open in Browser. I guess you're talking about Webhelp. Then you can follow Peter Grainge's site (grainge.org) and search for the snippet on Chrome.