function displayZoekservice(){
var leff = (screen.width - 600) / 2
var topp = (screen.height - 400) / 2
window.open('zoekservice.html','one','left=' + leff + ', top= ' + topp + ', width=600, height=400')
return false
}
function displayAdvies(){
var leff = (screen.width - 600) / 2
var topp = (screen.height - 600) / 2
window.open('advies.html','one','left=' + leff + ', top= ' + topp + ', width=600, height=600')
return false
}
function chatten(){
var leff = (screen.width - 475) / 2
var topp = (screen.height - 400) / 2
window.open('chatten.html','one','left=' + leff + ', top= ' + topp + ', width=475, height=400')
return false
}