Why?
The document contains images that are not in GIF or JPEG format, or are not correctly served by the Web server. Images in formats other than GIF or JPEG may not work on some mobile browsers.
How?
Convert with an image editor the said images either to GIF or to JPEG, depending on the type of images; Either update the links to these new versions, or use Content Negotiation to have both versions available and served depending on the browser capabilities.
Where?
Triggered by https://elearning.sut.ac.th/pluginfile.php/11/mod_forum/post/111194/pr_SUTmobile_app.jpg.
Triggered by https://elearning.sut.ac.th/pluginfile.php/162/user/icon/clean/f2?rev=883764.
Triggered by https://elearning.sut.ac.th/theme/image.php/clean/core/1440646535/i/course.
Triggered by https://elearning.sut.ac.th/theme/image.php/clean/core/1440646535/moodlelogo.
Triggered by https://elearning.sut.ac.th/theme/image.php/clean/forum/1440646535/icon.
More information
Severity: low
Useful improvements are possible.
Category: Rely on Web standards
In the highly fragmented market of devices and browsers, standards are the best guarantee for interoperability.
Best practice:
Send content in a format that is known to be supported by the device.