Why do we have different Google PageRank for / and index.jsp?

[q4web]

I noticed that most of Java websites own two different Google PageRank for "/" and "index.jsp" home page URLs. Here my first question is that why do we have two different pageranks for both urls when both relate to one page (homepage) - second question is that how can we make sure that each url (/ and index.jsp) has similar pagerank.

[Digeratist]

I think it's based on the number of external links to your site--something you have little to no control over. How many people link using just / vs. those who link with index.jsp.