Error in uploading pictures in the background of hotel webpage. Help programming experts! I can't understand the meaning of the code.

Your picture suffix is correct, but your format is not normal. For example, I can change a *. Txt file is converted into *. Gif file. The format is correct, but it won't open. This is not a valid gif file. ...

Generally, if the code is not rigorous, you can upload it directly, but if the programmer's code is rigorous, you will refuse to upload it. ...

Then there is the situation you face. ...