How to show the child div on mouse hover of parent div

If you want pure CSS than you can do it like this....

In the CSS below, on initialization/page load, I am hiding child element using display: none; and then on hover of the parent element, say having a class parent_div, I use display: block; to unhide the element.

.hotqcontent {
   display: none;
   /* I assume you'll need display: none; on initialization */ 
}

.parent_div:hover .hotqcontent { 
   /* This selector will apply styles to hotqcontent when parent_div will be hovered */
   display: block;
   /* Other styles goes here */
}

Demo

Try this

$(document).ready(function() {
  $('.parent_div').hover(function() { 
    alert("hello");
    $(this).find('.hotqcontent').toggle(); 
  });
});

Or

$(function() {
  $('.parent_div').hover(function() { 
    alert("hello");
    $(this).find('.hotqcontent').toggle(); 
  });
});

You can use css for this,

.parent_div:hover .hotqcontent {display:block;}