window.back() Fails in IE

<a href='http://www.codingforums.com/archive/index.php/javascript:window.back()' title='Go Back to Previous Page'>Back</a>
<a href='http://www.codingforums.com/archive/index.php/javascript:window.close()' title='Close this Pop-up Window'>Close</a>

In the above code Close works fine and Back works fine in Netscape. But in Internet Explorer 6 Back gives the error message:

"Object doesn't support this property or method"

Before I try Back I go from the first URL to a second so there will be something to go back to. The browser back arrow also works fine.

Thanks, Peter