Use local css file if link to online css file is dead

Question

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The problem:

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I am using w3.css(if you enter now w3schools.com site is down for maintenance) for styling my website.The problem

Answer 1

for check if w3.css is working you can use something like this. instead of src put w3.css image of logo or something .

function checkImage (src, up, down) {
    var img = new Image();
    img.onload = up; 
    img.onerror = down;
    img. src = src;
}

checkImage( "https://www.google.co.in/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png", function(){ alert("up"); }, function(){ alert("down"); } );