Check and adjust this first
Change the size of your image
Compress the file for best performance
Digital images have two kinds of size:
These are separate measurements, but both must be accounted for. (For our purposes, image dimensions are always expressed in pixels.)
Reducing the dimensions and the file size results in a smaller download for site visitors, meaning that the website will load and respond faster for them.
Images on your computer or camera are often larger than what is needed for your website/webpage. First make sure the resolution is correct.
Use the Marquee tool or edit the Canvas Size to crop your images to the needed size.
The Save for Web option compresses the image file for faster performance.