Edit in JSFiddle

Result
HTML
JavaScript

<body>
    <p>This is first paragraph element.</p>
    <p>This is Second paragraph element.</p>
    <p>This is Thire paragraph element.</p>
    <p>This is fourth paragraph element.</p>
    <p>This is five paragraph element.</p>
    <button id="myButton">Click Me</button>
    <button onclick="location.reload()">Reset</button>
    </body>

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