Reigel's demo page

HTML

<div id="left"></div>
<div id="right"></div>
<div id="top"></div>
<div id="bottom"></div>

CSS

body, html{
    cursor:crosshair;
}

#right {
    position: absolute;
    width:2000px;
    height:1px;
    background:#000;
}
#left {
    position: absolute;
    width:2000px;
    height:1px;
    background:#000;
}
#top{
    position: absolute;
    width:1px;
    height:2000px;
    background:#000;
}
#bottom{
    position: absolute;
    width:1px;
    height:2000px;
    background:#000;
}

JavaScript

$(document).bind('mousemove', function(e){
    $('#right').css({
       left:  e.pageX + 20,
       top:   e.pageY
    });
    $('#left').css({
       left:  e.pageX - 2200,
       top:   e.pageY
    });
    $('#top').css({
       left:  e.pageX,
       top:   e.pageY -1200
    });
    $('#bottom').css({
       left:  e.pageX,
       top:   e.pageY + 20
    });
});