Banner size (width x height in pixels), whether or not to adhere to corporate identity (primary colors, logo, slogan), the maximum size in Kb (according to the requirements of the site), the script is a banner (text, graphic elements).
Yes, of course. The main thing to decide whether to adhere to corporate style, as well as to know the size of the banner and the maximum weight in Kb (according to the requirements of the site).
Resize banner - change the size of the banner (the script remains the same).
It all depends on the complexity of the task. On average, more than a day.
Flash banner for more dynamic. Allow us to make a colorful animation. Gif banner in the usual case is simply a change of text and images without any additional effects. In most cases, used as a placeholder for flash banners (if the user has not installed flash player).