External links, that is to say the links that point to different sites from that of current site, should be reported properly as recommended by the W3C. This provides useful information to visitors while reading an article. Unfortunately this system is rarely implemented. The only known site that uses it is Wikipedia with a small icon:

Corrine's Security Garden is shown as external link in Wikipedia

In the above screenshot from Wikipedia reference, you can see respected Corrine’s blog as well as other external links are shown with typical icon beside each links.

This little trick is easily implemented using CSS rules. To begin we must add two properties to the CSS rule for hyperlinks:

a{
background:url("external.png") no-repeat scroll right top transparent;
padding:0 13px 0 0;
}


Nothing more simple, we add here an icon that is named external.png in the background of all the links. The padding is to shift the text in relation to the icon so they do not overlap.

Just now cancel the same rule for links that are not actually external links using attribute selectors in CSS:

a{
background:url("external.png") no-repeat scroll right top transparent;
padding:0 13px 0 0;
}
a[href*="blogname"]{
padding: 0;
background: none;
}


The second rule allows to specify new properties to links that contain the href attribute in the domain of our site. Here we remove the padding and background image. Texts made red should be changed.

Resource icons for external links

Right click to save them:

Note: Some are gif images, so remember to change both the name and extension in your CSS code.

Using external links with an icon for single page or post using span

As like our previous post, we can use the method for a single post or link too. But, the image must be in images folder of the current theme (to insert the URI path without http). The code becomes big though!

Is there WordPress plugin available?

Sure. WP External Links can handle and add icons.