Validation error

Why is the The W3C Markup Validation Service giving me this error now when i am checking pages i am working on, when it validated the same mark up a couple of months ago ?

I am using target=“_blank” to open links in a new window.
Is this the right way to do it, or is there a better way ?

Validation Output: 1 Error
Line 39, Column 273: there is no attribute “target”
…istrus+zebraThe+Perfectionist" target=“_blank”>Aquascaping for Hypancistrus ze…:email:
You have used the attribute named above in your document, but the document type you are using does not support that attribute for this element. This error is often caused by incorrect use of the “Strict” document type with a document that uses frames (e.g. you must use the “Transitional” document type to get the “target” attribute), or by using vendor proprietary extensions such as “marginheight” (this is usually fixed by using CSS to achieve the desired effect instead).

This error may also result if the element itself is not supported in the document type you are using, as an undefined element will have no supported attributes; in this case, see the element-undefined error message for further information.

How to fix: check the spelling and case of the element and attribute, (Remember XHTML is all lower-case) and/or check that they are both allowed in the chosen document type, and/or use CSS instead of this attribute. If you received this error when using the <embed> element to incorporate flash media in a Web page, see the FAQ item on valid flash.

It is new pages i am working on, here is the page for the error above;

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
   <title>Andrew's Hypancistrus Plecos</title>
   <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <link href="andrew's-hypancistrus-plecos.css" rel="stylesheet" type="text/css" />
   <meta name="google-site-verification" content="ipRYJuWdxjl952qVJuEzDn7YrXTYtESKrP1HdCAJ21Q" />
   </head>
   <body>
     <div class="wrapper">

         <div class="header">
	       <h1>Andrew's Hypancistrus Plecos</h1>
	     </div> <!-- end of header div -->

	     <div class="navigation">
		   <ul>
	         <li class="first"><a href="home.html">Home</a></li>
		     <li><a href="fish-hut.html">Fish Hut</a></li>
		     <li><a href="keeping.html">Keeping</a></li>
	         <li><a href="breeding.html">Breeding</a></li>
	         <li><a href="fry.html">Fry</a></li>
	         <li><a href="gallery.html">Gallery</a></li>
			 <li><a href="faq.html">F.A.Q.</a></li>
			 <li><a href="links.html">Links</a></li>
	       </ul>
         </div> <!-- end of navigation div -->

         <div class="bodycontent">
	       <h2>Home.</h2>
	         <p>Welcome to my website, i built this website to help provide information about keeping and breeding hypancisturs plecos.</p> <br />
		   <h3>Habitat.</h3>
	         <div class="image">
             <img src="images/amazon-basin-map.gif" width="300" height="300" alt="The Amazon River Basin." class="center" />
             <p>The Amazon Basin.</p>
	         </div>
			 <p>Hypancistrus plecos are found in the various tributaries of the Amazon river in Brazil, and also in the rivers of; Colombia, Venezuela, Guyana, Surinam and French Guiana.</p> <br />
			 <p>In their natural habitat hypancistrus are usually found in the vicinity of river rapids, in fast flowing water.</p>
			 <p>In the dry season the waters depth can be between 3 and 9 meters deep, whilst in the rainy season the waters depth can rise to between 10 and 18 meters deep.</p>
			 <p>The river bed is usually rocky with sandy patches, but also full of cracks and rocks that form a honeycomb structure, additionally there are tower-like rocks that rise from the river bed and extend upto two meters above the waters surface, which have a surface riddled with crevices, all of which provide numerous hiding places for the fish.</p> <br />
			 <p>A couple of great examples of a hypancistus biotope aquarium, is "Håvard Støre Andresen's" articles on Planet Catfish; <a href="http://www.planetcatfish.com/shanesworld/shanesworld.php?article_id=387title=Aquascaping+for+Hypancistrus+zebraThe+Perfectionist" target="_blank">Aquascaping for Hypancistrus zebra Part 1 - The Perfectionist</a> and <a href="http://www.planetcatfish.com/shanesworld/shanesworld.php?article_id=400title=Aquascaping+for+Hypancistrus+zebraThe+Rest+of+Us" target="_blank">Aquascaping for Hypancistrus zebra Part 2 - The Rest Of Us</a></p>

         </div> <!-- end of bodycontent div -->

	     <div class="footer">
		   <ul>
		     <li><a href="http://validator.w3.org/check?uri=referer"><img src="http://www.w3.org/Icons/valid-xhtml10" alt="Valid XHTML 1.0 Strict" height="31" width="88" /></a></li>
             <li><a href="http://jigsaw.w3.org/css-validator/check/referer"><img style="border:0;width:88px;height:31px" src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!" /></a></li>
             <li><a href="http://jigsaw.w3.org/css-validator/check/referer"><img style="border:0;width:88px;height:31px" src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS!" /></a></li>
		   </ul>
         </div> <!-- end of footer div -->

	 </div> <!-- end of wrapper div -->

   </body>
</html>

You’re using xhtml strict and so I doubt it validated correctly a couple of months ago because the target attribute has not been allowed in xhtml strict for a lot longer than that.

Use window.open instead.

target has never been allowed in strict as strict doesn’t allow you to have any frames or iframes to target and target was never really intended to open a new window (the second option down in the context menu when you right click on the link is for doing that).

Thanks for the replies.
I must have added the target attribute when tinkering with the web site after validating and never checked it again.

I will check out window.open.

That is assuming you actually want to try to make the external site open a popup window, which nowadays a lot of people will try and block or may not have JavaScript enabled on the browser. You’d be just as well using a standard link.