index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Generator Random RGB Color</title>
    <link rel="stylesheet" href="style.css">
    <link rel="icon" href="img/icon.png">
    <link href="https://fonts.googleapis.com/css?family=Radio+Canada:300,regular,500,600,700" rel="stylesheet"/>
</head>
<body>
    <div id="mainBox" class="mainBox">
        <input class="inputRGBText" id="mainInput" type="text" value="" readonly>
        <img id="copyBtn" title="скопировать текст" class="copyImg" src="img/copy.png" alt="img">
        <button id="mainbtn" class="randomButton">Get Random</button>
    </div>
    <script src="mainscript.js"></script>
</body>
</html>