Webpage Link Usability

A link points to a different page. That's a common perception. But wait, does this link point to a page of the same site, or an external site? Is the page open in the same window/tab, or in a new window/tab? Will the link change my current course of action? In addition, as AJAX technology has been adopted, many links actually bring up contents in a pop-up panel. We can see links do show different behaviors and users expect to know a bit of them before clicking on them.
Many of the links designed do not imply such information, especially those contextual links which are embedded in the content. A more usable design is to provide such hint to users, through the use of icons, text styles, pop-up tips, or even cursor styles. The design needs to consider providing these visual hints:
The target of links:

• within the same window but a different section (anchors), or
• in a pop-up panel/window, or
• open in a new window/tab

The source of content:

• linking to contents in the same site/application, or
• linking to contents in external sites, or

The type of content/link:

• reference content: provides relevant and brief content but does not change the current course of navigation.
• related content, which is part of the current course of navigation.
• triggering an action (actually a button, in some sense) such as hide/show, animation, etc.