To post photos they must be under 75kb. You need to open the picture in like wibdows paint and resize it and save it as a jpg.
Also you need to check and see what format the pictures are in, they need to be a jpg, because it's the smallest file size for a given image.
If you have the same picture in a jpg and another one in giff format, the giff is about 2/3's bigger in file size than the same picture in a jpg format.
With windows all you have to do is hold your mouse pointer on the picture and a window will pop up and tell you the size of the file, or right click and hit the properties on the picture to find out file size.