选中复选框后按钮可用，不选中不可用

<input type="checkbox" name="agree" id="agree" onchange="agree_change()" style="margin: 0px;">

<input id="toubiao_submit" onclick="kk()" disabled="disabled" type="button" class="toubiao_btn_disable" value="" title="提交"/>

function agree_change(){
  		if($("#agree").attr("checked")=="checked"){
  			$("#agree").attr("checked",false)
  			$("#toubiao_submit").attr("disabled",true);
  			$("#toubiao_submit").removeClass("toubiao_btn_able");
  			$("#toubiao_submit").addClass("toubiao_btn_disable");
  		} else {
  			$("#agree").attr("checked","checked")
  			$("#toubiao_submit").attr("disabled",false);
  			$("#toubiao_submit").removeClass("toubiao_btn_disable");
  			$("#toubiao_submit").addClass("toubiao_btn_able");
  		}
	}