In the trac.ini configuration section, the use of whitespace between multiple comma separated entries in urls is not allowed. Most plugins allow whitespace between entries in configuration file parameters.
[tractab]
names=Google,My Blog
urls=http://www.google.com,http://blogs.acceleration.net/russ
perms=WIKI_VIEW,TRAC_ADMIN
The following should be a valid configuration,
[tractab]
names = Google, My Blog
urls = http://www.google.com, http://blogs.acceleration.net/russ
perms = WIKI_VIEW, TRAC_ADMIN
Presumably whitespace is not allowed between entries for the other parameters as well, but I haven't tested this.