Edit in JSFiddle

Result
HTML
JavaScript

<body>
    <ul type="square">
    <li>Cesc Fabregas</li>
    <li>Thierry Henry</li>
    <li>Lionel Messi</li>
    <li>Ronaldinho</li>
    <li>Zinedine Zidane</li>
    </ul>
    <button id="myButton">Click Me</button>
    <button onclick="location.reload()">Reset</button>
    </body>

$(document).ready(function()
    {
    $("#myButton").click(function()
    {
    $("ul li:lt(2)").css({'font-size':'20px','background-color':'Orange'});
    });
    });