When governments become States parties to a convention, they can identify that they will not be bound to particular elements of that treaty. This is known as "entering a reservation" and in the CEDAW Convention this is permitted under Article 28. Sometimes States parties can also make declarations. These have the same effect as reservations.
Nevertheless, there are limits to this process: Article 28(2) precludes any reservation that is incompatible with the object and purpose of the CEDAW Convention. Furthermore, reservations are meant to be temporary so that a States party can take steps to remove obstacles to the implementation of the articles it has reserved.
Countries have filed many formal reservations to the CEDAW Convention. In fact, it is the most heavily reserved treaty in the UN human rights system. Many of the reservations address key elements of the CEDAW Convention, including the nature of steps to be taken to eliminate discrimination (particularly Article 2) and the primacy of existing family law codes (particularly Article 5 and Article 16). Additionally, a number of States parties have reserved against the resolution of disputes on interpretation or application of the CEDAW Convention by the International Court of Justice (Article 29).
The UN maintains a database with all the reservations here. There you can also access objections to reservations made by other States parties.