i would recommend irfanview from IrfanView.com, it is a very popular graphics viewer and will enable you to resize an image and/or reduce its size for use on the web

i use it regularly and have been very happy with it

cheers

serge

ps one way to reduce the size of an image is to reduce its dpi to 72 as it is more than enough for web pages, dpi stands for 'dots per inch'