This type of disclaimer is common. The Code of Federal Regulations is more current than the USC, but some titles still lag behind the print version. Oddly enough, the CFR Web site contains no disclaimer. Still, I wouldn't cite to the online version. Through Findlaw and each of the 50 states' official Web sites, I researched the availability, searchability, currency and official status of state statutes and administrative codes.
All states provide at least a portion of their statutes and codes on the Web.
Several states do not provide this information at all. Some only note the year through which the statutes are current. Some states provide copyright dates, but this is different from revision dates. Just because the state has copyrighted the statutes as of 2000 does not mean that the statutes on the Web are current up to 2000. Many states provide disclaimers on their statutory Web sites, reminding the viewer that the Web version of the statutes does not constitute the official version.