Hi
you need this java code for your purpose. add code between your <body> , </body> tag:
<a href="#"><img src="Your Image Path.jpg" width="120" height="80" border="0" onclick="MM_openBrWindow('http://www.google.com','your_page_name','width=300,height =200')" /></a>
Description
img src="Your Image Path.jpg" width="120" height="80"
=> Your Image Size
('http://www.your_target_page.com','your_page_name','width= 300,height=200')
=> Your target page with size that you like
I hope this help