Edit in JSFiddle

function init() {
    // Instanciate sigma.js and customize rendering :
    var sigInst = sigma.init(document.getElementById('graph')).drawingProperties({
        defaultLabelColor: '#fff',
        defaultLabelSize: 14,
        defaultLabelBGColor: '#fff',
        defaultLabelHoverColor: '#000',
        labelThreshold: 10,
        defaultEdgeType: 'curve'
    }).graphProperties({
        minNodeSize: 0.5,
        maxNodeSize: 15,
        minEdgeSize: 1,
        maxEdgeSize: 1,
        sideMargin: 50
    }).mouseProperties({
        maxRatio: 32
    });

    // Parse a GEXF encoded file to fill the <graph></graph>
    // (requires "sigma.parseGexf.js" to be included)
    sigInst.parseGexf('https://dl.dropboxusercontent.com/u/9598149/facebook.gexf');
     
    // Draw the graph :
    sigInst.draw();
}

if (document.addEventListener) {
    document.addEventListener("DOMContentLoaded", init, false);
} else {
    window.onload = init;
}

<div id="graph"></div>

#graph {
    background: #222;
    position: absolute;
    width: 100%;
    height: 100%;
}