if (document.images) {
        var button1off = new Image();
        button1off.src = "images/button1_off.gif"
        var button1on = new Image()
        button1on.src = "images/button1_on.gif"
        
        var button2off = new Image()
        button2off.src = "images/button2_off.gif"
        var button2on = new Image()
        button2on.src = "images/button2_on.gif"

        var button3off = new Image()
        button3off.src = "images/button3_off.gif"
        var button3on = new Image()
        button3on.src = "images/button3_on.gif"

        var button4off = new Image()
        button4off.src = "images/button4_off.gif"
        var button4on = new Image()
        button4on.src = "images/button4_on.gif"

        var button5off = new Image()
        button5off.src = "images/button5_off.gif"
        var button5on = new Image()
        button5on.src = "images/button5_on.gif"

        var button6off = new Image()
        button6off.src = "images/button6_off.gif"
        var button6on = new Image()
        button6on.src = "images/button6_on.gif"

}

function act(imgName) {
        if (document.images) {
                document[imgName].src = eval(imgName + 'on.src')
        };
}

function inact(imgName) {
        if (document.images) {
                document[imgName].src = eval(imgName + 'off.src')
        };
}