In our contemporary tab centric browsing experience —where tabs have become all but common place for navigating the web, it might appear helpful to provide your user a new tab for opening external content, thus saving them the task of pressing the back button to return to your site, but this is not always the case.
POUR Guidelines and Accessibility
The POUR guidelines were defined under the Web Content Accessibility Guidelines 2.0 specification which was drafted by the W3C in 2008. POUR stands for Percieveable, Operable, Understandable, and Robust. Opening links in new tabs infringes on the second principal of Understandability, which states that websites should operate in easy to understand and predictable ways.
Imagine for a moment that you are a blind user using a screen reader to navigate content when you arrive at a link midway down the page, as soon as you click on the link a new tab appears beside your current window without you knowing and you are left wondering where your content is. As you can imagine this can be a very disorienting experience for blind clients using your site. This particular point is specifically addressed by the W3C Content accessibility guidelines.
UX Considerations
Opening links in news tabs also takes away control from the users by eliminating their ability to choose how links open. In the Smashing Magazine article “Should links open in new windows?” Vitaly Friedman states that:
Users need to be able to rely on consistency of the user interface and know that they won’t be distracted or disrupted during the interaction. Users must know, understand and anticipate what is going on and what will happen once user interface elements are used. Any deviations from this convention result in a more design-oriented and less user-oriented design.
By dictating to users how their browsers ought to behave you rob them of the freedom to decide how they want to navigate the web.
Setting Link Behavior in WordPress
Now that we’ve discussed why you shouldn’t open links in new tabs, lets discuss how to set link behavior so that we can avoid this problem altogether. In WordPress you set link behavior on a post by post basis and must set the behavior for each link included in your post. To set link behavior we must first create a new link:
1. First highlight the text you would like to link to.
2. Then press the link icon on the visual editor.
3. In order to set link behavior look for the check-box under the title text field. By default this should be unchecked. Unchecked means that the link will open in the current tab, this is the behavior that we want.
4. Make sure that the check-box remains unchecked.
5. Click update at the bottom of the window when you are done.
Please note that this tutorial is specific for WordPress, other web publishing platforms will require different steps.
For further discussion on the practice of opening new links in tabs please visit:
ClarkWP WordPress Magazine 
This seems totally counter-intuitive both a logical and commercial perspective.
Really? Seriously, frustrating your users by having links open in the background where they can’t see it or didn’t know it opened, or having it redirect to the opening tab or window and interfere with their reading is better?
Doesn’t matter. It’s the law in most countries, not opinion. It has nothing to do with logic nor commercial perspectives. It is the law, and like speeding, while it is still the law, and you have the potential to do harm when you break it, it’s up to you to risk breaking it. And breaking it runs the risk of fines and a lawsuit if the law in the country in which your site is hosted has any enforcement.
Can you point me to the statute that governs this in your jurisdiction. I would be interested to read it.
This article has many resources that reference the laws in different countries. The United States uses the P.O.U.R. Guidelines and standards as well.
Thanks for that.
I have realised that we may be talking at cross-purposes here since I agree that opening new tabs for internal links is very frustrating whereas opening new tabs for external links seems to me counter-intuitive, as I originally stated. I shall be interested to read these guidelines.
Thanks. This applies to all links.