In every case, when you apply for a green card for your spouse, be advised that the permanent residency for your spouse will be conditional for two years. Within 90 days of your second wedding anniversary, you and your spouse must apply to the USCIS to have the permanent residency become permanent.
from here:
http://www.uscitizenship.info/blog/us-citizenship-and-marriage
When a person receives a green card based on a marriage that is less than 2 years old when the person becomes a permanent resident, then the resident status is Conditional for two years. At the end of the two years, the resident status expires unless a petition to remove the condition is approved by the BCIS.
The petition to remove the condition is signed by both the husband and the wife. It is possible for a divorced spouse to sign the petition alone and then have the condition removed if it is proved that the marriage was genuine and not a sham.
The BCIS will consider a petition which is signed by the conditional resident alone only if the marriage has ended (usually by divorce)...in other words, a separated couple cannot have the condition removed unless both sign the petition or they end the marriage.