Loading please wait for message in javascript custom button on a standard page

var divback, divpop, img;

if (document.getElementById(‘popDiv’) && document.getElementById(‘backDiv’) && document.getElementById(‘myImg’))
{
divpop = document.getElementById(‘popDiv’);
divback = document.getElementById(‘backDiv’);
img = document.getElementById(‘myImg’);
divback.style.display = ‘block’;
divpop.style.display = ‘block’;
img.style.display = ‘block’;

}
else
{
// Create a background and show the image on top
divpop = document.createElement(‘div’);
divpop.id = ‘popDiv’;
divpop.style.backgroundColor = ‘white’;
divpop.style.borderWidth = ‘0px’;
divpop.style.borderRadius = ‘5px’;
divpop.style.zIndex = ‘9998’;
divpop.style.left = ‘50%’;
divpop.style.top = ‘50%’;
divpop.style.width = ‘115px’;
divpop.style.height = ’50px’;
divpop.style.position = ‘fixed’;
divpop.style.marginLeft = ‘-25px’;
divpop.style.marginTop = ‘-25px’;
document.body.appendChild(divpop);

img = document.createElement(‘img’);
img.id = ‘myImg’;
img.src = ‘/img/loading24.gif’; // your spinner gif
img.style.top = ‘50%’;
img.style.position = ‘fixed’;
img.style.zIndex= ‘9999’;
img.style.left = ‘50%’;
img.style.marginLeft = ‘-12px’;
img.style.marginTop = ‘-12px’;

var div1 = document.createElement(‘div’);
div1.id = ‘msgDiv’;
div1.style.float = ‘right’;
div1.style.marginTop = ’18px’;
div1.style.marginRight = ’20px’;
div1.style.fontSize = ’12px’;
div1.style.fontWeight = ‘700’;
div1.innerHTML = ‘Loading…’;

/* Append loading gif image in parent div */
divpop.appendChild(img);

/* Append message div in parent div */
divpop.appendChild(div1);

divback = document.createElement(‘div’);
divback.id = ‘backDiv’;
divback.style.backgroundColor = ‘black’;
divback.style.opacity = ‘0.80’;
divback.style.filter = ‘alpha(opacity = 30)’;
divback.style.position = ‘fixed’;
divback.style.width = ‘100%’;
divback.style.height = ‘100%’;
divback.style.top = ‘0’;
divback.style.left = ‘0’;
divback.style.zIndex = ‘9997’;
document.body.appendChild(divback);

}
write here your salesforce or sforce code here.