Sessions problems

[Guest]

When someone browses or searches my site normally everything is OK and they will end up with a session ID like:

http://xxxxx.com/product_info.php?products_id=70220&osCsid=53ca5d337879c4dfa40977e3a8116282

 

The problem is if I have given a link to a product either in an email or on the index page and when the visitor clicks this they lose their session so may end up at:

http://xxxxx.com/product_info.php?products_id=70220&osCsid=

 

This means anything that was in their basket is lost. How can I write html links so that it will remember the session ID.

 

I'm using oscommerce CRE Loaded 6.

 

thanks