js achieve Top features of the solution

<span style="font-size:14px"><p id="back-to-top"><a href="#top"><span></span>返回顶部</a></p></span>  

# Back-to-Top { 
    position: Fixed; 
    the display: none; 
    bottom: 100px; 
    right: 80px; 
} 
# Back-to-Top A { 
    text-align = left: Center; 
    text-Decoration: none; 
    Color: # d1d1d1; 
    the display : Block; 
    width: 64PX; 
    / * used in CSS3 transition property to add the text hoplinks gradients * / 
    -moz-transition: Color lS; 
    -webkit-transition: Color lS; 
    -o-transition: Color lS ; 
} 
# A Back-to-Top: hover { 
    Color: # 979 797; 
} 
# A Back-to-Top span { 
    background: transparent URL (/static/imgs/sprite.png?1202) NO-REPEAT -25px -290px ; 
    border-the RADIUS: 6px; 
    Run the display: Block; 
    height: 64PX;
    width: 56px; 
    margin-bottom: 5px; 
    / * used in CSS3 transition property to the < span > Add gradients * / label background color 
    -moz-transition: background lS; 
    -webkit-transition: background lS; 
    -o-transition : background lS; 
} 
# A Back-to-Top: hover span { 
    background: transparent URL (/static/imgs/sprite.png?1202) NO-REPEAT -25px -290px; 
}

< Script the src = "http://ajax.microsoft.com/ajax/jQuery/jquery-1.7.2.min.js" > </ Script > 
< Script > 
$ ( function () {
         // when the position of the slider is at 100 pixels from the top of the jump link appears, disappears or 
        $ ( function () { 
            $ (window) .scroll ( function () {
                 IF ($ (window) .scrollTop () > 100 ) { 
                    $ ( " # Top-to-Back " ) .fadeIn ( 1500 ); 
                } 
                the else 
                { 
                    $ (" # The Back-to-Top " ) .fadeOut ( 1500 ); 
                } 
            }); 

            // When you click a link to jump back to the top of the page position 
            $ ( " # the Back-to-Top " ) .click ( function () {
                 // $ ( 'body, HTML') Animate ({scrollTop: 0}, 1000);. 
        IF ($ ( ' HTML ' ) .scrollTop ()) { 
                $ ( ' HTML ' ) .animate ({scrollTop: 0 }, 1000 );
                 return  to false ; 
            } 
            $ ( 'body').animate({ scrollTop: 0 }, 1000);
                 return false;            
           });       
     });    
});
</script>