How Can I Write Tamil In Facebook?

The best tool to use is the Google Transliteration; now this is not to be mistaken with Google translate which just translates word for word (well as best as possible). This offers to convert the sound of the words from one alphabet to another so it converts characters to the phonetic equivalent in your language and in your case, it would be Tamil. First, you select the language you require and then you start typing a word just the way it would sound in Tamil but using English letters.  When you have finished one word you separate it by a space, you will see that the word is immediately translated into your language and script.  The tools supplied enable you to format and edit so you can change the colour of the text or add hyperlinks.  As not every web tool from Google is perfect, they have designed a function that corrects not finding the exact translation which arises in the form of a list of suggestions in a drop down menu.  There is also an advanced editing option that can help you further with character-by-character development.
Another tool that is quite widely used to convert the Indian languages is Quillpad. This is a free online editing tool and is very simple in its application. The website offers free membership with newsletter, there is a coded widget that you can have on your website and they also offer support if necessary. The one downside is that it is not supported by Microsoft Word, as Word does not support the Indian Unicode by default but this can be resolved by installing the Supplemental language Support which is provided.

Just type Tamil.

You need rephrase your question dear !