SharePoint provides different levels of permissions, from the “Full Access” to “Limited Access”. Last one is not documented clearly and designed to cover some side-effects of item’s hierarchy.
Cite from “Permission levels and permissions” article:
“The Limited Access permission level is designed to be combined with fine-grained permissions to give users access to a specific list, document library, item, or document, without giving them access to the entire site. However, to access a list or library, for example, a user must have permission to open the parent Web site and read shared data such as the theme and navigation bars of the Web site. The Limited Access permission level cannot be customized or deleted”
“Limited Access” allows no direct access to site content at all, but is intended to allow users to traverse the site in order to access the items within it that they have explicit permissions to see.
For example, the user might have access only to one page of a site, but still need access to style sheets and other supporting site infrastructure in order to view it. In that case the user would need “Limited Access” permissions on the site and “Restricted Access” to the page.
Current “SharePoint Tips and Tricks” series has been moved to its own “SharePoint SandBox” site,to leave the place for others SharePoint posts on this blog