reset id column

Question

I have a table and i need to insert data and delete data from the table but when i delete one data its id is also deleted i need to enter data in the id number in sequence. for example if i have 3 records and i have deleted third record from database then that data will not be inserted in 3rd number id, its id will be 4 but i want to insert it with the id 3.plz help me