Do you want this to display on every single page on your website or only on certain pages?
As for an example the following works.
<div style="position:fixed;top:100px;right:10px;border:1px solid black;background-color:#CCC">
This div is fixed to the screen and will scroll up/down with the screen
</div>
This creates a box aligned to the right of the browser screen that will always stay 100px down from the top of the window and 10px to the right of the browser window.
position:fixed is what keeps it moving with the screen when your scroll down/up.
top:100px; is what places it 100px down from the top of the browser screen
right:10px; is what places it 10px from the right of the browser screen
The border and background-color stuff is to just apply some styling to the box so you can see it.
The above code only works on a single page though and if you would like to place this button on more than one page there is a better way to go about it using external CSS instead of inline CSS. The above code was to just give you an idea.
If you need more help let me know.
