Plone has been standardising internal links without a trailing slash "/" at the end. It is good to follow that standard, for both SEO reasons and data collection.
Links to pages and images should be like this:
/plone_basics/adding_internal_links, and NOT like this:
/plone_basics/adding_internal_links/ (in the first case, the terminating "/" is not there)
Note 1: when linking in blog entries which can have different urls it is best to add the full link like e.g /blog/archive/2006/08/26/atimage-tips
Note 2: Plone wysiwyg content editors can automatically change the format of links to:
../../blog/e.t.c which is very bad. It is advisable to either use reStrucutredText, or Dreamweaver if you really need to use HTML still.
Images are the same: .. image:: /images/vasudevaserver.gif
This is bad: /images/vasudevaserver.gif/
The bottom line is: Never add a trailing slash!
Also, please make sure images always have the type of file at the end (.jpg or .gif)