Hi ,
I am a student who has graduated with a masters degree in California and I have a job in virginia . I am on a F1 status and my optional practical training commences on the 26th of oct 09. I was wanting to know as in how much tax deductions are the students on optinal practical training subjectable for ? I exactly have no idea as in how much of my salary would be going in as taxes .
Thanks for reading this long question.!

On F1/OPT you are exempt from residency for 5-years. You must file non-resident tax return Form 1040NR or 1040NR-EZ and Form 8843.

Your income is not subject to FICA taxes but you must pay federal and state income taxes. On your OPT income you will get deduction based on tax treaty between the U.S. and your country.
Your U.S. Tax Return: U.S. Tax Filing Requirements for Non-Residents

Redundant question; already answered.