Many Applicants for Benefits Can Check Case Status Using the Internet
When you receive an I-797 Notice of Action form from the USCIS for your filed immigration forms it will have a receipt number. Most of the time this number will be preceded by 3 letters (such as EAC, LIN, SRC, WAC, or MSC), although some do not have these letters. Using this receipt number you can find the status of your USCIS petitions/applications online. This service, known as My Case Status, enables speedy and efficient monitoring of the USCIS process without having to call or otherwise contact the USCIS directly.
The possible stages for a form to go through in this process are: Acceptance; Initial Review; Request for Evidence (boo!); Request for Evidence Response Review; Testing and Interview; Decision; Post Decision Activity; Oath Ceremony (naturalization); Card/Document Production. Not every case will go through every one of these steps. It is possible to not receive a request for evidence for example, and aliens filing forms I-140 will not have an oath ceremony since they are not seeking citizenship at the time of filing.
The online system also allows and alien to check on the processing times for different types of forms at different service centers and field offices. This information will give an alien a good idea of how long he/she will have to wait for a decision to be made on his/her case.
The My Case Status website can be found here.