_open: function( event, target, content ) {
        if ( !content ) {
            return;
        }

        // if we have a title, clear it to prevent the native tooltip
        // we have to check first to avoid defining a title if none exists
        // (we don't want to cause an element to start matching [title])
        // TODO: document why we don't use .removeAttr()
        if ( target.is( "[title]" ) ) {
            target.attr( "title", "" );
        }

        // ajaxy tooltip can update an existing one
        var tooltip = this._find( target );
        if ( !tooltip.length ) {
            tooltip = this._tooltip( target );
            target.attr( "aria-describedby", tooltip.attr( "id" ) );
        }

        // attach the target to the tooltip
        tooltip.data( 'target', target );

        tooltip.addClass( this.options.tooltipClass || "" )

        tooltip.find( ".ui-tooltip-content" ).html( content );
        tooltip
            .stop( true )
            .position( $.extend({
                of: target
            }, this.options.position ) )
            .hide();

        this._show( tooltip, this.options.show );

        this._trigger( "open", event, { tooltip: tooltip } );

        this._bind( target, {
            mouseleave: "close",
            blur: "close"
        });
    }

    _tooltip: function( element ) {
        var id = "ui-tooltip-" + increments++,
            tooltip = $( "<div>" )
                .attr({
                    id: id,
                    role: "tooltip"
                })
                .addClass( "ui-tooltip ui-widget ui-corner-all ui-widget-content " );
        $( "<div>" )
            .addClass( "ui-tooltip-content" )
            .appendTo( tooltip );
        tooltip.appendTo( document.body );
        if ( $.fn.bgiframe ) {
            tooltip.bgiframe();
        }
        this.tooltips[ id ] = element;
        return tooltip;
    }