Thank you folks for the valuable time you took to solve my issue.
i just found the problem.
the problem is just above the group of this check boxes, an un closed </lable> tag is what caused all the problem
<label><strong>COMBINATOR</strong>// << <font color='"#FF0000"'>Lable not closed, this is what caused the problem
Please select few charactors and click generate.<br />
<span class="style1">*Selecting more than 7 characters is not recommended</span>
<div id="alpha" style="border:1px solid black;">
<input type="checkbox" name="A" id="A" />
<input type="checkbox" name="B" id="B" />