iPhone doesn't show image generated by aspx website

i want to develop an iPhone optimized website, which includes an generated image. To generate the image i call an external website (aspx). Example:

https://url/filedownload.aspx?documentid=1234&mimetype=image/jpeg

This is no problem on any standard browser on the pc, the imag开发者_StackOverflowes shows up after 2 seconds. But on the iphone there is only the blue question mark showing.

The resultion is ~ 170 * 100 72dpi.

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This is certainly a server-side issue, as suggested - a working link or a sample of the source is needed to help resolve. In the meantime, some other things to check; does the image type created match that of the content type specified?

I would then try adding the exact same image (as a static physical file) to the website, load this in an iPhone (to prove there is nothing fundamentally wrong with the image file data) and then compare response headers from your dynamic image code to ensure they are the same - do you require attachment-filename for example?