There are a few different, common image formats. There even exists different types of some of these formats. Most notably, the jpeg/jpg image format has a couple of different types. One is best suited for print media and the other is best suited for web media.
On occasion, your browser may come across a web page that contains a "print media" type jpg file and your browser may not know how to display this item. This has been known to happen both while using Internet Explorer and Firefox. To date, jpg file formats seem to be prone to this issue and other image file types appear to not be.
For information on the different image files types, why different formats exist, and what the best file type to use for your purposes is, visit the following:
The easiest way to fix this is to create a copy of the image file and then optimize the copy for the web. Most advanced graphics editors, such as Photoshop, Paintshop Pro, and GIMP, have the ability to create a web optimized image. Typically this feature is found in some sort of File toolbar item of the application of choice. Microsoft Paint does not have this capability.
After the image has been optimized, upload it to your web page and test it out.