IIT JEE will undergo massive change in its format from 2013 onwards.
Those who wish appear IIT's undergraduate entrance test (named as JEE Advanced) will have first clear JEE Main which is to be conducted by CBSE from the year 2013 onward.
Apart from the IITs, National Institutes of Technology, the Delhi Technological University and other centrally funded technical institutes (CFTIs), all colleges in Gujarat and Nagaland-the only two states to join the JEE (Main) this year -will screen students based on their marks in the JEE (Main).
CBSE will conduct the JEE Main. Those who are in the top 20% in their respective 12th board exams and qualify the JEE Main can take the JEE (Advance) exam for admission to the IIT’s, which will be conducted by IIT's itself.
A student can attempt JEE Advance two times at maximum. As you have missed one chance to appear for IIT-JEE, you have only one chance left.
To know more details about JEE exams, click here