css实现将网页变成黑白色

.gray { 
    -webkit-filter: grayscale(100%);
    -moz-filter: grayscale(100%);
    -ms-filter: grayscale(100%);
    -o-filter: grayscale(100%);
    filter: grayscale(100%);
    filter: gray;
}

<svg version="1.1" xmlns="http://www.w3.org/2000/svg">
    <filter id="grayscale">
        <feColorMatrix type="matrix" values="0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0"/>
    </filter>
</svg>

filter: url(gray.svg#grayscale);

<script src="http://james.padolsey.com/demos/grayscale/grayscale.js"></script>

/*js调用*/
grayscale(document.getElementById("thisImage"));
/*jq调用*/
grayscale($("#thisImage"));