Its safe :)
Or you could try this way
1. Try this alternative link from your phone's browser:
http://chess.com/mobile/bin/www.chess.com/Chess.com.jad
That alone solves the problem for many users.
However, if that doesn't work and you are still getting errors, you may have better luck installing the application via computer:
2. On your computer's browser, open this link: http://chess.com/mobile/bin/www.chess.com/Chess.com.jar
3. Download the file and save it on your computer
4. Transmit file "chess.com.jar" to your mobile phone from the computer - using a cable, bluetooth, card-reader, etc.
5. Install on your phone
i AM ABOUT TO ENTER MY MOBILE NO. TO DOWNLOAD FOR MOBILE. IS THIS SAFE, AND MY CREDIT WILL NOT BE JEOPARDISED OR MY PHONE HACKED?
I WANT TO KNOW THAT IT IS SAFE. THANK YOU.