It looks like the CSS hasn't been updated on the server -- it's still trying to reference the .jpg version.
That being said, you can't just change the text extension of files like that -- you need to have the extension match the format the image is saved as. For photos, you should be using PNG or JPG format, with the correct .png or .jpg extension. The reason it was not showing in some browsers is that was most likely saved in GIF format, but labeled with a .jpg extension, which will cause things to go a bit haywire.