The colors in these photos are different because of different color profile used by the browsers.
When you render your photo Adobe Photoshop automatically (or by default) sets the color profile to Adobe RGB. This setting has a much wider spectrum or gamut on the color wheel (red, green, yellow). Adobe sets it with this default because printers will read the wider gamut and it is therefore better for printing.
When web programmers designed the standard browsers they decided to have have the browsers spectrum the same as the universal display gamut. This gamut is known as the working sRGB on photoshop. sRGB is a much smaller color spectrum that is used in television, monitors and other displays. When we, as photographers render out photos, photoshop displays it as Adobe RGB and if you have a Mac like me my monitor displays those extra colors. The problem is when you import it into flickr or a website. What the browser/internet site will do is strip the original color profile and reassign it with sRGB.
