AuthUserFile /dev/null AuthGroupFile /dev/null AuthName "CU Boulder Only" AuthType Basic <Limit GET> order deny,allow deny from all allow from .colorado.edu </Limit>(Leave an extra blank line at the bottom of the file, lest the server think the last tag is incomplete...)
The above would limit access (to all files in the same directory) to only browers on *.colorado.edu computers. One can permit access from specific computers as well as domains; for example, the following .htaccess would permit access from the specified computers (2 from Colorado State, 1 from MIT) and from any computer at CU Boulder:
AuthUserFile /dev/null AuthGroupFile /dev/null AuthName "CU Boulder Only" AuthType Basic <Limit GET> order deny,allow deny from all allow from banach.colostate.edu allow from newton.colostate.edu allow from snoopy.mit.edu allow from .colorado.edu </Limit>