Javascript Firefox Addon new Textwindow in the corner

Question

I want Javascript to generate a new "area" on the top right corner. In this "area" I want to have some text and maybe a few url's.

What I got so far:

var x = document.createElement("TEXTAREA");
var t = document.createTextNode("Sample Text");

x.style.cssFloat='right';
x.appendChild(t);
document.body.appendChild(x);

But the textfield looks not like I want it to look like. The first problem I got is that it is transparent, which it should not be.

Do I just have to add some more CSS attributes or would it be better to use another function to create that area?

I am using SDK/jpm to generate a Firefox Addon.