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ok, dh wo genau in dem code mussid="an"
muss im HTML stehen und in dem HTML, das Du gepostet hast, ist es drin:
<span style="cursorointer; display : block" onclick=
"document.getElementById('text2').style.display='block';document.getElementById('an').style.display='none';document.getElementById('zu').style.display='block'" id="an">mehr</span>