Edit in JSFiddle

<div class="bottom_post">
    <div class="ad">
        <cite>SPONSORED LINK</cite>
        <div class="googlead">広告的な…</div>
    </div>
    <ul class="share">
        <li>
            <a class="button1">button1</a>
        </li>
        <li>
            <a class="button2">button2</a>
        </li>
        <li>
            <a class="button3">button3</a>
        </li>
        <li>
            <a class="button4">button4</a>
        </li>
    </ul>
</div>

.bottom_post {
    display: block;
    height: 320px;
}

div.ad {
    float: left;
}

.googlead {
    width: 336px;
    height: 280px;
    border: 1px solid black; 
}

ul.share {
    float: right;
    list-style: none;
}

.button1 {
    background-color: red;
    width: 70px;
    height: 70px;
    display: block;
}

.button2 {
    background-color: cyan;
    width: 70px;
    height: 70px;
    display: block;
}

.button3 {
    background-color: yellow;
    width: 70px;
    height: 70px;
    display: block;
}

.button4 {
    background-color: green;
    width: 70px;
    height: 70px;
    display: block;
}