function tema1(){
    document.body.style.background="url(imgs/bg1.jpg) #000 repeat top left";
    texto.style.color="#ffffff";
}
function tema2(){
    document.body.style.background="url(imgs/bg2.jpg) #fff repeat top left";
    texto.style.color="#000000";
}
function tema3(){
    document.body.style.background="url(imgs/bg3.jpg) #fff repeat top left";
    texto.style.color="#000000";
}