$(document).ready(function(){  

$(".button1").hover(function() {$(this).attr("src","http://www.theeater.nl/images/but1b.jpg"); }, function() {   
$(this).attr("src","http://www.theeater.nl/images/but1a.jpg");});

$(".button2").hover(function() {$(this).attr("src","http://www.theeater.nl/images/but2b.jpg"); }, function() {   
$(this).attr("src","http://www.theeater.nl/images/but2a.jpg");});

$(".button3").hover(function() {$(this).attr("src","http://www.theeater.nl/images/but3b.jpg"); }, function() {   
$(this).attr("src","http://www.theeater.nl/images/but3a.jpg");});

$(".button4").hover(function() {$(this).attr("src","http://www.theeater.nl/images/but4b.jpg"); }, function() {   
$(this).attr("src","http://www.theeater.nl/images/but4a.jpg");});

$(".button5").hover(function() {$(this).attr("src","http://www.theeater.nl/images/but5b.jpg"); }, function() {   
$(this).attr("src","http://www.theeater.nl/images/but5a.jpg");});

$(".button6").hover(function() {$(this).attr("src","http://www.theeater.nl/images/but6b.jpg"); }, function() {   
$(this).attr("src","http://www.theeater.nl/images/but6a.jpg");});

});