There is no citation type for URLs, per se, in the standard BibTeX styles, though Oren Patashnik (the author of BibTeX) is considering developing one such for use with the long-awaited BibTeX version 1.0.
The actual information that need be available in a citation of an URL is discussed at some length in the publicly available on-line extracts of ISO 690-2; the techniques below do not satisfy all the requirements of ISO 690-2, but they offer a solution that is at least available to users of today's tools.
Until the new version arrives, the simplest technique is to use the
howpublished field of the standard styles' @misc function. Of
course, the strictures
about typesetting URLs
still apply, so the entry will look like:
@misc{...,
...,
howpublished = "\url{http://...}"
}
Another possibility is that some conventionally-published paper, technical report (or even book) is also available on the Web. In such cases, a useful technique is something like:
@techreport{...,
...,
note = "Also available as \url{http://...}"
}
There is good reason to use the url or hyperref
packages in this context, since (by default) the \url command
ignores spaces in its argument. BibTeX has a habit of splitting
lines it considers excessively long, and if there are no space
characters for it to use as 'natural' breakpoints, BibTeX will
insert a comment ('%') character ... which
is an acceptable character in an URL, so that \url will
typeset it. If you're using url, the way around the problem
is to insert odd spaces inside the URL itself in the .bib
file, to enable BibTeX to make reasonable decisions about breaking
the line. Note that the version of \url that comes with recent
versions of the hyperref package doesn't suffer from the
'%-end of line' problem: hyperref
spots the problem, and suppresses the unwanted characters.
A possible alternative approach is to use the harvard
package (if its citation styles are otherwise satisfactory for you).
Harvard bibliography styles all include a "url" field in
their specification; however, the typesetting offered is somewhat
feeble (though it does recognise and use LaTeX2HTML macros
if they are available, to create hyperlinks).