While sending my tax return my computer went off line, how can I be sure it was received by turbo tax????

If you e-filed, make sure the return was e-filed successfully and accepted. To find out this information see the information below:
https://shop.turbotax.intuit.com/efile/efile_status_lookup.jsp

If accepted, you should be able to track your return by the below information:
http://www.irs.gov/Refunds  

You complete your tax return by finishing all 3 Steps in the File section.  In Step 3, to e-file your tax return, you must click on the large Orange button labeled "Transmit my returns now".  

After completing the File section and e-filing your tax return you will receive two emails from TurboTax.  The first email when your tax return was transmitted and the second email when the tax return has either been accepted or rejected.

Use this TurboTax website to check the status of an e-filed return and if it was either accepted or rejected