Clck to see EXAMPLE
1. Very important is your length to width ratio. It needs to be 1 to 1, ie a square.If you need to, use the crop tool to get the correct size.
2. The width, dimension can not be less than 1600 px
3. The image quality needs to be 90 or better
all of these perameters are options in Adobe Photshop's Save for Web and Devcies dialogue box.
Found by going to File > Sve for Web & Devices
options seen there are:
"quality" remeber should be 90 or better
"width" "height" rember the width should be no less than 1600px and the hight should equal the width.
If you do not have Photoshop Microsoft Picture Manager is a very good alternative. Use your searchbox to located it on your computers hard drive. I seen it saved in odd places.