В чем ошибка?
<div id="kar"><img src="img\mozg2.png" width="100%" height="70%"> <p class="nadpis">Мозг</p></div>
<div id="kar"><img src="img\yho.png" width="100%" height="70%"><p class="nadpis">Уши</p></div>
<div id="kar"><img src="img\nose.png" style="margin-left:5px" width="70%" height="70%"><p class="nadpis">Нос</p></div>
<div id="kar"><img src="img\yazik2_2.png" style="margin-left:5px" width="90%" height="70%"> <p class="nadpis">Язык</p></div>
<div id="kar"><img src="img\glaz3.png" style="margin-left:5px" width="90%" height="70%"> <p class="nadpis">Глаза</p></div>
var nadpis = document.getElementsByClass('nadpis');