s.gif is a one dot image. And I can see strings like "GIF89a����!�,D;". I thought it's the valid gif data and tried to transfer the data with $.ajax. But this is the second question.
The first thing I cannot explain is, if I visit "http://www.izhaiyiqi.com/ce/tbtfscom/tbcaps/s.gif" directly, it returns "R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==" which seems to be something Base64 encoded. Why isn't it a valid image bytes array? I pretty sure that the image is OK.
Below is the snapshot of request header from Chrome.