$(document).ready(function(){
function preload(arrayOfImages) {
    $(arrayOfImages).each(function(){
        $('<img/>')[0].src = this;
        // Alternatively you could use:
        // (new Image()).src = this;
    });
}

// Usage:

var baseUrl = 'http://www.mednutra.com/';

preload([
    baseUrl + 'images/slider_in_back.png',
    baseUrl + 'images/logo.png',
    baseUrl + 'images/portfolio_pics/homeopathic_back.jpg',
    baseUrl + 'images/portfolio_pics/herbals_back.jpg',
    baseUrl + 'images/portfolio_pics/nutritional_back.jpg',
    baseUrl + 'images/portfolio_pics/patented_back.jpg',
    baseUrl + 'images/portfolio_pics/welcome_back.jpg',
    baseUrl + 'images/big_picture_1.png'
]);

});