Questions Basic Image Work

• Which of the following image types should be used on the web - png, gif, jpg, bmp, psd, eps? Why?
• Why is it important to assign height and width to images? alt?
• What's the difference between an "alt" and a "title" attribute ?
• Why would it be a bad idea to use xhtml to resize (scale) an image? How should an image be resized?
• How do you make an image "float" to the left or right?