Get scroll value and then return to it on click

JavaScript
1

I want to…

(1) Get the current browser scroll position/value when clicking this:
<a href=“#menu”>MENU</a>

(2) Return to the last stored scroll position when click this:
<a href=“#top”>RETURN TO CONTENT</a>
…with #top being a non-JS fallback

I can do everything to complete this, it’s just the getting and setting of the browser scroll value I could do with some help on.

…and most importantly to do this without jQuery (or any other library).

I also want it to be completely cross-browser compatible.

2 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">

<head>
  <title></title>
</head>

<body>
 <div style="height:300px;" ></div>
 <a href="#menu">MENU</a>
 <div style="height:300px;" ></div>
 <a href="#menu">MENU</a>
 <div style="height:1300px;" ></div>
 <a href="#top">RETURN TO CONTENT</a>
<script type="text/javascript">
/*<![CDATA[*/

function zxcScrollTo(o){
 var oop=zxcScrollTo,as=document.getElementsByTagName('A'),z0=0;
 for (;z0<as.length;z0++){
  if (as[z0].href&&as[z0].href.indexOf(o.AnchorHREF)>0){
   as[z0].onclick=function(){
    oop.lft=window.innerHeight?window.pageXOffset:document.documentElement.clientHeight?document.documentElement.scrollLeft:document.body.scrollLeft;
    oop.top=window.innerHeight?window.pageYOffset:document.documentElement.clientHeight?document.documentElement.scrollTop:document.body.scrollTop;
    return false;
   }
  }
  if (as[z0].href&&as[z0].href.indexOf(o.LinkHREF)>0){
   as[z0].onclick=function(){ window.scrollTo(oop.lft,oop.top); return false; }
  }
 }
 oop.top=0;
 oop.lft=0;
}

zxcScrollTo({
 AnchorHREF:'#menu',
 LinkHREF:'#top'
});
/*]]>*/
</script>
</body>

</html>

I can add an animated scroll if required