tedster - 12:56 am on Oct 12, 2010 (gmt 0)
...that link points to http://www.example.com/page_B.html. The beginning slash means "start at the domain root". That's true no matter what the URL of the source page may be.
... this link resolves differently in different cases. Without the beginning slash, the full URL begins with the directory where the source page "lives".