font-family: "zw", serif, sans-serif;
I was still having the trouble displaying Chinese characters properly despite the fact that I've followed the instruction described in this thread. Out of luck, I have made it work on my e-Reader. Just in case someone out there has the trouble like I did, the solution that worked for me is above. I have changed the "DroidSansFont" to "zw". I found 'zw' as a font class in the stylesheet.ccs file. I don't know why it works but it works now.