used to use frames, to provide an outline of sections on the left. The new interface uses a pull-down menu across the top to get to the same pages.
An interface that looks like the older interface is still available at:
The new pages all end with an x. For example the new start page is cccbdb.nist.gov/introx.asp.
The old style interface is cccbdb.nist.gov/intro.asp.