Preload image 

Method 1
Basic concept. Load image when page is loaded

%MINIFYHTML8d2a2526e3447df8b5e4639a34090cce15%


Method 2
Improve method 1. Create function

function preload(images) {
    if (document.images) {
        var i = 0;
        var imageArray = new Array();
        imageArray = images.split(',');
        var imageObj = new Image();
        for(i=0; i<=imageArray.length-1; i++) {
            //document.write('');// Write to page (uncomment to check images)
            imageObj.src=images[i];
        }
    }
}

usage

%MINIFYHTML8d2a2526e3447df8b5e4639a34090cce16%

Method 3
Create 1 pixel image and hiding it somewhere in your page

Method 4
similiar like method 3 but hide it using css

%MINIFYHTML8d2a2526e3447df8b5e4639a34090cce23%