Why I am unable to play mp4 videos on Sony ericsson c905a?

Alright dear, as you said that you are not able to ply mp4files to your Sony Ericsson mobile phone, so I suggest you to please convert the mp4 file in less resolution because I guess your phone supports only the lower version of mp4 files, you just need a good video converter so I want to tell you please convert all your videos with the help of ultra video converter.Download ultra mp3 software from the internet and install it on your computer system and then from the converter menu select your device and convert the video,for example you have the Sony Ericsson mobile then you have to select the Sony Ericsson phone model from the ultra video converter and then you can easily convert the video, and believe me this converted video runs on your mobile, I think this my little information helps you to get the video mp4 for your device.