+ <a href="javascript:zoom(-10);" title="zoom_out" onclick="click(this);"><img src="resources/zoom-out.png" /></a>
+ <a href="javascript:zoom(0);" title="zoom_in" onclick="click(this);"><img src="resources/zoom-100.png" /></a>
+ <a href="javascript:zoom(10);" title="zoom_in" onclick="click(this);"><img src="resources/zoom-in.png" /></a>