Attempts to upload the same .jpg I use for my Twitter account is reject with the following response from Twitter:
It seems you did not upload a valid Image.
Only PNG, GIF and JPEG formats are supported.
The image I attempt to upload is the same image that my current Twitter account displays as follows:
file name: davidwbrown.jpg
size: 3.7 K
The Twitter dev page displays allowed image sized as: 700K
What to do?