Thanks for your reply. i did found a similar code in js forum.
<select onchange="if(selectedIndex != 0) location = options[selectedIndex].value;">
<option>< select an option ></option>
BUT, i still have one issue. In First page, it works fine, when i click on Wood and it jumped to the new page. The same thing happened when i branch back from Wood page to this page. As Wood is still selected in the drop down list, when i click again on wood, it didn't trigger the onchange event, therefore it didn't jump there. How can i set the default to 'select and option' everytime when i branch out or in from other page to this page ?
thanks in advance