If the bar you wish to implement is the orange tool bar then you could design the bar in CSS inside of a div, like , and then you can see I have made the display none which will hide the div element. Then, once you have content you want to put inside of this tool bar you can easily use jQuery to say
$('#flash-notice').text("Text to put into the flash notice").show().fadeOut(5000);
This would set the text, set the display to block which will display the flash div and then you can add features like fadeOut to have the tool bar fade out.
Let me know if this was helpful, I can probably provide more details if needed. Tools used: HTML, CSS (any version is fine), and jQuery.