<!doctype html>
<style>
    .test {
        width: 200px;
        height: 100px;
        margin-left: 90px;
        border: solid 10px blue;
    }

    .spacer {
        float: left;
        width: 90px;
        height: 120px;
        background-color: blue;
    }

    .outer {
        width: 200px;
        height: 100px;
        margin-left: 90px;
        padding: 10px;
        background-color: blue;
    }

    #gradient1 {
        width: 200px;
        height: 100px;
        background-image: linear-gradient(to right top, black 49%, white 50%);
    }

    #gradient2 {
        background-image: linear-gradient(to right top, black 49%, white 50%);
    }

    #gradient3 {
        background-image: radial-gradient(ellipse at 30% 30%, black 49%, white 50%);
    }
</style>

<div>
    <div class="spacer"></div>
    <div class="outer">
        <div id="gradient1"></div>
    </div>
</div>
<div id="gradient2" class="test"></div>
<div>
    <div class="spacer"></div>
    <div id="gradient3" class="test"></div>
</div>