GIMP is a free photo editing program that works on most operating systems and in many languages. It is very similar to other photo editing programs out there, so hopefully you can adapt this article to fit your needs.

Once you have GIMP downloaded and installed open your image in GIMP.

From here you want to resize your image by going Image > Scale Image. I enter my width of 400px and hit enter - the height will automatically scale to 300px. NOTE: you want your image to automatically scale; different cameras/pictures are going to result in different image sizes. GIMP will most likely show "X resolution" and "Y resolution" as 72 pixels/in. IF NOT, be sure to set one resolution or the other to 72 (the other will automatically change for you).

Now it's time to save. File > Save As, enter a file name and hit Save. A new box is going to open; this is where you can reduce the image quality to 80%.

Hit Save again and you're done! Your image is now ready to upload to your website.