<img id="img_1" src="주소" alt="설명"  style="display: none" />

<img id="img_2" src="주소" alt="설명"  style="display: none" />

<img id="img_3" src="주소" alt="설명"  style="display: none" />

<img id="img_4" src="주소" alt="설명"  style="display: none" />

<img id="img_5" src="주소" alt="설명"  style="display: none" />

<script type="text/javascript">

var rand_num = Math.floor(Math.random() * 5) + 1;

document.getElementById('img_'+rand_num).style.display = 'block';

</script>

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