Intro

I was having issues on using some websites. It was not getting rendered properly.

Fixes

1. Installing a Firefox Addon

Actually, installing this add-on did fix the issue.
https://addons.mozilla.org/en-US/firefox/addon/instant-malayalam/

2. Fixing by installing fonts at system level

sudo apt install fonts-smc

Above package is meta package, it install a lot of fonts. Just use apt search fonts-smc-* to find individual font name.

Conclusion

Doing either Fix 1 or 2 solves the problem for me. But, 2nd one seems to be good one if you're on Linux.