Most of these computers, laptops, tablets and Smartphones used to have all the important Tamil fonts if they have the Windows operating system. If you know the Tamil fonts name you can buy them online with out any difficulty. On the other hand most of the Tamil web sites used to provide a link to download and use it for to read that Tamil web site.
Also there are plenty Tamil Font CD's available in the computer shops. You can buy from them and can install them in your computer, laptop, tablet or Smartphone very easily with some commands.
How to install Tamil fonts in your computer, laptop, tablet or Smartphone?.
Paste the font in the desktop. This is to find the place of the font easily when installing it. You can open the zip file or copy past from the source and place it in the desktop.
Go to your Control panel.(You can go there easily through "Start" menu.)
Open the Fonts folder there.
On the left hand side top you will see file. Click to open the drop down menu and select "Install new font.
This will open the Add font box.
In the folder select desktop by going through the correct path.
You can see the font once you opened the desktop folder.
Select the font (Which will be shown in the list of fonts) and press OK.
The new font will be installed in to your font folder. There after you can delete the font from ther desktop.