function retweet() {
    var bitly_id  = 'gorimaru';
    var bitly_key = 'R_e957e8cdc55014e2d84024e716dbc35b';

    api = 'http://api.bit.ly/shorten'
        + '?version=2.0.1'
        + '&format=json'
        + '&callback=retweetCallback'
        + '&login=' + bitly_id
        + '&apiKey=' + bitly_key
        + '&longUrl=';
        
    var script = document.createElement('script');
    script.type = 'text/javascript';
    script.src = api + encodeURIComponent(location.href);
    document.body.appendChild(script);
}
function retweetCallback(json) {
    var tid = 'gorimaru9';
    var d = document;
    var w = window;
    var l = location;
    var e = encodeURIComponent;
    var sel = '';
    if ( d.selection ) {
        sel = d.selection.createRange().text;
    } else if ( w.selection ) {
        sel = w.selection.createRange().text;
    } else if ( d.getSelection ) {
        sel = d.getSelection();
    } else if ( w.getSelection ) {
        sel = w.getSelection();
    }
    var f = 'http://twitter.com/home/?status='
          + e( sel+' RT @'+tid+': "'+d.title+'" '+json.results[location.href]['shortUrl']);
    if( !w.open(f,'retweet') ) {
        l.href = f;
    }
}