Skyrunner

Thumbnail link to large picture full code

The complete code you want is...

<a href="http://www.siteyouwanttogoto.co.uk" target="_blank"><img src="nameofyourpicture.jpg" width="119" height="94" border="0" alt="Visit this amazing site or whatever you want to say"></a>

Explanation

The target="_blank" will open the new site in a new window, so your visitor won't be leaving your site.

The img src="nameofyourpicture.jpg" is the file name of your picture, followed by it's size in pixels. (Size not essential, but your page will load far better if sizes are specified.)

The alt tag is where you can write what goes in that little bubble that appears when your visitor holds his mouse pointer over your link.

Make sure you get all the flags... < > inverted comas and equal signs in the right places, and it should work a treat.