My first opinion is it's break the separation of content and behavior. and new link in new window will make browsing difficult for screen reader user.

I personally do not like to open web content pages in window, but if client want then we will have to do.

From usability point of view

consider the following two situations where a user doesn’t know upfront if the site opens links in new windows or in the same window:

1. user wants to open link in a new window, but the site opens links in the same window,
2. user wants to open link in the same window, but the site opens links in new windows.

In the first situation users can choose to open a link in the new window using context-menu or shortcuts described in the next sections of this article. In this situation users are the initiators of actions as they decide how the linked page should be displayed. Here site’s behavior meets user’s expectations resulting in a good user experience.

In the second situation users would simply click on the link and suddenly find out that the link is opened in a new window. In this situation users are the responders of actions as they need to react on the way how the linked page is displayed — for instance close the windows which was opened automatically. Furthermore, here site’s behavior doesn’t meet user’s expectations resulting in a bad user experience.

Users find it annoying when the site does something without asking them to do so. If users want to open new windows let them do so and don’t indulge their intelligence by making decision for them otherwise. Don’t force a new window upon users unless there’s a very good reason to do so.

reference - http://www.smashingmagazine.com/2008/07/01/should-links-open-in-new-windows/

and

Believe if or not, there are instances when using a new window is a good idea, such as when:

• The link is for a document, such as a PDF or Word file. Opening a new window will allow the image or document to download in the background. It also prevents users from accidentally closing the browser window when they close the document.
• The link is for a large image. In this case, a new window allows the Web user to keep a browser window open while the image is being downloaded.
• The link is for a printable version of an article or Web page. Here, a new window allows users to keep the current window open while they print the article or page in the background.

Source - http://articles.sitepoint.com/article/beware-opening-links-new-window

My first opinion is it's break the separation of content and behavior. and new link in new window will make browsing difficult for screen reader user.

I personally do not like to open web content pages in window, but if client want then we will have to do.

From usability point of view

consider the following two situations where a user doesn’t know upfront if the site opens links in new windows or in the same window:

1. user wants to open link in a new window, but the site opens links in the same window,
2. user wants to open link in the same window, but the site opens links in new windows.

In the first situation users can choose to open a link in the new window using context-menu or shortcuts described in the next sections of this article. In this situation users are the initiators of actions as they decide how the linked page should be displayed. Here site’s behavior meets user’s expectations resulting in a good user experience.

In the second situation users would simply click on the link and suddenly find out that the link is opened in a new window. In this situation users are the responders of actions as they need to react on the way how the linked page is displayed — for instance close the windows which was opened automatically. Furthermore, here site’s behavior doesn’t meet user’s expectations resulting in a bad user experience.

Users find it annoying when the site does something without asking them to do so. If users want to open new windows let them do so and don’t indulge their intelligence by making decision for them otherwise. Don’t force a new window upon users unless there’s a very good reason to do so.

reference - http://www.smashingmagazine.com/2008/07/01/should-links-open-in-new-windows/

and

Believe if or not, there are instances when using a new window is a good idea, such as when:

• The link is for a document, such as a PDF or Word file. Opening a new window will allow the image or document to download in the background. It also prevents users from accidentally closing the browser window when they close the document.
• The link is for a large image. In this case, a new window allows the Web user to keep a browser window open while the image is being downloaded.
• The link is for a printable version of an article or Web page. Here, a new window allows users to keep the current window open while they print the article or page in the background.

Source - https://www.sitepoint.com/beware-opening-links-new-window/