Many websites still uses the attribute target=”_blank” which links to external pages. From several discussions on this topic on blogs and forums, apparently there is a very large number of people uses target=”_blank” as an essential method.
The Google Web Authoring Statistics show that the target attribute is generally used very often and it is presumed by Google that most _blank target attribute actually used in addition to the almost ubiquitous use of href, around half of pages in the sample had at least one a element with a target attribute (Determining whether these are mostly attempts to make open links in new windows or tabs or whether they are indicative of frames use would require further research, the first seems most likely, however, since frames in general are not used much).
One can assume that up to 30-50% website uses target=”_blank =” regularly. We are not innocent: in our outgoing links too.
Why the attribute target = “_blank” is used?
The main reason is the fear that visitors can be lost. That is, if the user clicks on an external link without this attribute, the target page opens in the same window, and the visitor will not return to the source. If _blank is used, then the main page still remains open, and the user will always return to the source page.
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What is the disadvantage?
It should also be noted that this attribute is not approved in the XHTML Strict version.
Conclusion
- All browsers have a “back” button with which the last visited page can be called. This “one-page-back” functionality is also available on the keyboard (e.g. in Windows via Alt + Left Arrow), also some current mice has extra buttons to go back one page.
- Opening new windows prevents the relation to the original page, the visitor can not understand from which link it has brought the new page.
- Modern browsers offer a ‘tabbed browsing’, opening a new window when clicking a link here is often perceived as a nuisance or is necessary to set the options to expire.
- Visitors when have a page with an interesting information, the site certainly will not forget when he/she clicks an external link. If the information has addressed the attendees, this will certainly take the side according to a bookmark or come back after the call of the external link again.
- Many find it annoying when a Web page for each external link is a force _blank, and a new browser window or a new tab is opened by one. There may be occasional circumstances in which the visitors to open a link in a new window or tab wish, but it can control the visitors themselves (such as Windows and IE / Firefox / Opera: Hold down the Shift key while on a Link clicks).

I went through a “phase” where I was using _blank in each article. Then I read that most people find that irritating. I do, however, have links in the sidebar (i.e., the link to here) programmed with _blank. I even use those links myself to visit favorite blogs. :)
90% webmasters (including WordPress users) not have the main problem of W3C xHTML strict validation because almost uses xHTML transitional, which is a perfect blanket of people unaware of how to correct xHTML strict. Transitional, however allows almost anything from old codes like , _blank etc.
I checked your source code, you are using xHTML strict like me, this is nice. As xHTML strict does not allow _blank, we actually need to use javascript to open them in new Window to keep error free.