Change CSS property on click on buttons?

Hy, Please can any one help me to do this task. i really need it so much.

i want to change the class style of the button (witch is a link) by clicking on it. The buttons are contained on a dynamic child div witch will change every time. the name of the dynamic child div will stay the same every time.

Note: Only one single child div will displayed in the parent div.

This is the style code:

.btn_child              {display:block;  margin:-1px; border:1px solid; background-color:#428bca; border-color:#357ebd; text-align:left; padding-left:15px;  line-height:30px; }
.btn_child:hover        {background-color:#3276b1; border-color:#285e8e; }
.btn_child_selected     {background-color:#3276b1; border-color:#285e8e; }

This is the html code:

<div id="parent" class="parent_class"> 
<!--this is a dynamic content and the ID will change. only the name will still the same-->
<div id="dynamic_child1" name="child">
<a class="btn_child" target="_blank" href="" > link1        </a>
<a class="btn_child" target="_blank" href="" > link2        </a>
<a class="btn_child" target="_blank" href="" > link3        </a>
</div>
</div>

IMPORTANT: By clicking on the next button, the old one will return to default style and the new one style will be changed.

This is a link. it may explain more: http://ift.tt/1GJ8nCd