javascript这样为什么就不能调用？该如何解决

javascript这样为什么就不能调用？
<script   language= "javascript "   type= "text/javascript ">
              function   Back()
{
                window.history.go(-1);
}
        </script>

        <asp:Button       id= "Button2 "       style= "background:   url(Normal/tool-bkgd.jpg)   repeat-x;   BACKGROUND-IMAGE:       url(LookOut/cancel.gif);       BACKGROUND-REPEAT:       no-repeat; "       runat= "server "       Text= "取消 "   Width= "79px "   OnClientClick= "return   back(); "> </asp:Button>


[解决办法]
楼上正解