gistfile1.txt

$(document).ready(function() {

//Get the window height and width
var winH = $(window).height();
var winW = $(window).width();
/*Here 200 is your divs (check) hight replace it with your required hight alos make required changes at style.*/
 $("#body").css('margin-top', winH/2 - 469/2);

/*Here 300 is your divs (check) width replace it with your required width alos make required changes at style.*/
 $("#body").css('margin-left', winW/2 - 990/2);



//Definimos los backgrounds
changeBackground();
//setInterval(changeBackground,5000);
blink_uno();

//Solucionamos k cuando hagan click en el li haga el link
$("#header li").click(function(){
     var $this = $(this);
     $this.find("a").click();  
     return false;
});

});

function blink_uno() {
document.getElementById('blink').style.visibility='visible';
setTimeout('blink_dos()',500);
}
function blink_dos() {
document.getElementById('blink').style.visibility='hidden';
setTimeout('blink_uno()',500);
}


function changeBackground(){
    
 var randBack = Math.floor((Math.random()*3)+1); ;   
 var img = 'img/slide'+randBack+'.jpg';
 $("body").css({background: 'url("'+img+'") no-repeat center center fixed'}); 
 $("body").css({'background-size': 'cover'}); 
    
}