You should strip the complete image in very tiny parts. For example; the cancel button should be split in a 1px,1px square (repeat it in the css) and convert it to .PNG or if possible take only the css from it, right click on the layer -> copy css.
To avoid high loading or huge broadband usage, you should not take the whole image and put it on your website. This will also not be responsive friendly, if you would like to make it responsive.