var str_task = document.createElement("div");
str_task.className = "DeskTop_Task_List";
str_task.attachEvent("onmouseover", function(){ButtonMouseOver(this)});
str_task.attachEvent("onmouseout", function(){ButtonMouseOut(this)});
str_task.className = "DeskTop_Task_List";
str_task.attachEvent("onmouseover", function(){ButtonMouseOver(this)});
str_task.attachEvent("onmouseout", function(){ButtonMouseOut(this)});
str_task.attachEvent("onmouseover", function(){ButtonMouseOver(this)});
str_task.attachEvent("onmouseout", function(){ButtonMouseOut(this)});
str_task.className = "DeskTop_Task_List";
str_task.attachEvent("onmouseover", function(){ButtonMouseOver(this)});
str_task.attachEvent("onmouseout", function(){ButtonMouseOut(this)});
==>
var str_task = document.createElement("<div class='DeskTop_Task_List' onmouseover='ButtonMouseOver(this)' onmouseout=ButtonMouseOut(this)'></div>");
用document.body.appendChild(str_task);就正常。用document.getElementById("DeskTopTask_List").appendChild(str_task);就不可以了。