WordPress增加返回顶部效果的方法

<script src="top.js" type="text/javascript" charset="utf-8"></script >
<div id="scroll"><a href="javascript：void(0)" onclick="goto_top()" title="返回顶部">TOP</a></div>

//<![CDATA[
var goto_top_type = -1;
var goto_top_itv = 0;
function goto_top_timer()
{
var y = goto_top_type == 1 ? document.documentElement.scrollTop : document.body.scrollTop;
var moveby = 15;
y -= Math.ceil(y * moveby / 100);
if (y < 0) {
y = 0;
}
if (goto_top_type == 1) {
document.documentElement.scrollTop = y;
}
else {
document.body.scrollTop = y;
}
if (y == 0) {
clearInterval(goto_top_itv);
goto_top_itv = 0;
}
}
function goto_top()
{
if (goto_top_itv == 0) {
if (document.documentElement && document.documentElement.scrollTop) {
goto_top_type = 1;
}
else if (document.body && document.body.scrollTop) {
goto_top_type = 2;
}
else {
goto_top_type = 0;
}
if (goto_top_type > 0) {
goto_top_itv = setInterval('goto_top_timer()', 50);
}
}
}
//]]>

/*返回顶部*/
#scroll {display:block; width:30px; margin-right:-380px;
position:fixed;
right:50%;
top:90%;
_margin-right:-507px;
_position:absolute;
_margin-top:30px;
_top:expression(eval(document.documentElement.scrollTop));
}
#scroll a {
display:block;
float:right;
padding:9px 5px;
cursor: pointer;
background-color:#444;
color:#fff;
border-radius:5px;
text-decoration: none;
font-weight:bold;
}
#scroll a:hover {
background-color:#333;
color:#669900;
text-decoration: none;
font-weight:bold;
}