Juvenile Jail Improvement Act - Revises provisions of the Juvenile Justice and Delinquency Prevention Act of 1974 to authorize the Administrator of the Office of Juvenile Justice and Delinquency Prevention, through 2001, to promulgate regulations making exceptions to the prohibition against detaining or confining a juvenile in an adult jail or lockup with respect to a juvenile accused of a nonstatus offense who is awaiting an initial court appearance. Permits such juvenile's detention or confinement in a State approved portion of a county jail or secure detention facility for up to 72 hours. Provides that such exceptions are limited to areas that: (1) are outside a Standard Metropolitan Statistical Area and have no existing acceptable alternative placement available that is easily accessible; (2) permit the same staff members to oversee both juveniles and adults if such staff members have been properly trained and certified to supervise juveniles; and (3) ensure that juveniles have no regular contact with adults who are incarcerated because they have been convicted of a crime or are awaiting trial on criminal charges.