My first H1B was expiring on 04/24/2010. so i applied for H1B extension in November and i got my H1B extension approved on Jan 5th from 04/26/2010 to 04/25/2013. Will I be out of status for that 1 day(04/25/2010)? Should I carry the additional documentation that was mailed to USCIS that we already asked for correction in case if we receive revised petition after 04/25/2010?
 
As long as the extension was properly filed (evidenced by a Receipt and the receipt date on the Approval Notice), you would not be considered out of status. Carry the original receipt with you when you travel.