My website is loading slowly. I've check the performance with Pingdom. It shows that images cost 80%+ loading time. Some unnecessary images was loaded (Not included in index). Please tell me how to solve or optimize it.
Also, how to let it just load a small size images for post thumbnails & original size for feature image in the post. Now, there no option for me to set picture qualities(thumbnail, low, medium, high). It means all picture will be shown as original size whatever it is a preview / cover.