There are six styles provided by harvard which are compatible with natbib.
The command \harvardurl only format the style of the url. The output of the url is defined in the used bst file.
As an example of one of the six styles I use the file agsm.bst to demonstrate the behavior.
The file agsm.bst has the following code:
FUNCTION {write.url}
{ URL empty$
{ skip$ }
{ "\newline\harvardurl{" URL * "}" * write$ newline$ }
if$
}
If the entry of the url is empty you will get no output. Otherwise you get the output:
\newline URL formated with \harvardurl \newline
To avoid the output of the url you must modify the bst file.
Please note: Never change the original bst file. Make a copy of the needed bst in your working directory and modify this new file.
harvardpackage in addition tonatbib? – Mico Jan 14 '12 at 17:08