If you are using a large image file size which is many megabytes (MB) in size for your website and you are using web design tools like wordpress, or etc to do re-size of the image. It will not change the file size of the image file even though the image display is now becomer smaller.
To fix this, you will need to resize your images in a graphics editor (ie. Photoshop Elements, MS Paint, Gimp) before you upload the image.
