[css-div="height: ???px; width: ???px; background-color: #??????; opacity: 1.0"] *text here* [/css-div]
Just add the height and width of how you please. The width is usually the width of the banner, and the height is a bit more than the banner's height, but it has additional length so you can add your text in. The background colour, you can get the hex-code from either using photoshop, or maybe google or if you wanted just black you can put 000000. And the rest is self explantory.