PLEASE help with a simple animated sliding div! Options

[bossythecow1924]

Hi I am new to web design and even more so to javascript, which is what I believe to be the easiest way to solve my problem. I want to make a div with fixed height and width properties "slide" onto my page as soon as the page loads and have it "rest" between my header and the horizontal nav bar underneath - horizontally centered under my header as well. No other animation necessary, this is a simple banner with one line of text and a solid background color. I have tried combing the web for premade code but I cannot find anything remotely close to what i want.

Does anyone know of a website with a script like this?

or

Can anyone put me on the path to creating this in JS myself? (i know i said im a noob but im a quick learner as well )

html and css files links:

 nporthomelayout.css ( 5.52k ) Number of downloads: 379
 home.html ( 12.74k ) Number of downloads: 391


!!! as a side note, I would like to keep a margin around the proposed sliding div similar to what I have already to keep the margins similar throughout the page.

Thank you for taking your time to read this and free money to anyone that replies!!!!!!!!!!!!!