File with webm and ogv extension not found, why?

Question

Yii

I have files in the folder
/video/file.mp4
/video/file.webm
/video/file.ogv
If I insert example.com/video/file.mp4 in the browser, then the video opens,
if example.com/video/file .webm or example.com/video/file.ogv - 404 not found. Why 404? They are physically