, or other information
which, if followed, leaves you worse off than you would have been without it. For instance, if you have a hard disk crash
and lose work, someone might recommend that you keep all your files on floppy disk
instead. Given that floppies are less reliable than hard disks, this advice is worse
Out-of-date software documentation is often worse than useless. For a while, ISC was distributing an old version of the BIND FAQ along with BIND. The FAQ documented the obsolete named.boot file format, which the BIND named no longer understood. One could follow the FAQ and write a named.boot file, only to find that no amount of careful debugging would make named accept it -- it expected the new named.conf format. Thus, this FAQ could be regarded as worse than useless.
A tool may also be worse than useless. For instance, using the wrong size screwdriver on a Phillips screw may not only fail to drive the screw in, but also strip it. One could even, in a fit of annoyance, refer to some people's "help" as worse than useless.