A general warranty deed is a type of deed where the grantor (seller) guarantees that he or she holds clear title to a piece of real estate and has a right to sell it to the grantee (buyer). The guarantee is not limited to the time the grantor owned the property—it extends back to the property's origins. A General Warranty Deed includes six traditional forms of Covenants for Title. Those six traditional forms of covenants can be broken down into two categories: present covenants and future covenants.
Note - Not all states recognizes the Covenant of Further Assurances (e.g. Ohio)
Most people hire someone to perform a title search to determine if there are defects that must be resolved before they purchase real property. They can also purchase title insurance, which covers many types of losses that occur if problems are discovered later, but title insurance raises a number of other legal issues. http://www.bankrate.com/brm/news/mortgages/20040826a1.asp