Noel,
the red x in the box is a picture place marker used by the browser to show it could not load the picture.
I have a copy of Paint Shop Pro (PSP) that I use to get the images from my camera down to a size for posting. There are two parts to this, the size in pixels on the screen and the file size. If you are using Micro$oft Internet explorer, try this.
Find one of my pictures, right click it and select properties, it will give you the dimensions (I use 512*384 or 384*512) and the size of the file. The JPG file format uses a lossy compression to reduce the file size. I set it to 50% in PSP, my pictures are 20-30K in size and I think still have enough detail. This should work on most pictures, letting you check the sizes. (It does not work in the gallery).
Hope this is useful, ask if you need more help 8)