Firefox will read all the unicode fonts without any problem..
But some times it will not render some proprietary fonts such as manorama, karthika, tikkana, hemalatha etc. They are dynamic fonts.
In such situation , here we have an extension in firefox called Padma. We will get it as an add-on of firefox.
Method of installation:
1. Click tools menu of firefox and select add-ons.
2. Then get extensions –>browse all add-ons.
3. search for padma and add it to firefox.
4. restart your firefox.
5. Now you solved your problem….