need help with website updates

    I was told you are great on this chatboard and I am hoping
    someone here can help me.
    I created a website for my classroom and when I update the
    pictures on the site it looks fine from my computer. But
    when I open it from another computer (like I did at school
    today) it does not show the updates. I googled my site
    and the followed the link and it showed the updates. I am
    a newbie at this and I must be doing something wrong.
    Please help if you can.
    Thanks so much :o)