Disable F12 key in the browser

When user press F12 key, browsers developer tool bar will open in the below portion of the browser. By
using the developer tool bar user can see the design, javascript code and corresponding css applied to the controls in the page. To prevent the user to do that we will the hide developer tool bar.

You can use the below code to do that. Write the below code in the head section of the page.
<script type="text/javascript">

document.onkeydown = function (event)
{
     event = (event || window.event);
     if (event.keyCode == 123 || event.keyCode == 18)
     {
           alert("This function is disabled here");
           return false;
     }
}
</script>