Open new windows for non-web documents

Jakob Nielsen says links to non-web documents should be opened in a new browser window because users can become confused by the different interface of a PDF document, for instance, than that of a web page:

In user testing, we often observe the following behavior: When people are finished using PDF files, Word memos, PowerPoint slides, Excel spreadsheets, and similar documents, they click the window’s close box instead of the Back button. This gets them out of the document all right, but not back to the Web page from whence they started.

This advice seems to conflict with Nielsen’s own previous guideline of not opening new windows for web users, but he says it does not because “users don’t view a PDF file as being the same environment as a website.” Therefore Nielsen says to open non-web documents in a new window, warn users before doing so, and remove any browser toolbars (such as the back button) on the new window.

Implementing this is no problem if your web page is XHTML Transitional. Simply append target="_blank" to any link tag. But what about XHTML Strict? I found that the solution has already been reduced to three options at SimpleBits.

My method is to use XHTML Transitional if I must have links open in new windows. Sometimes I have used XHTML Strict with JavaScript, but it’s important to keep in mind that if JavaScript is turned off in the user’s browser the link will open in the current window.