The game images are blurred when I set viewport's width to device-width

I add the viewport setting in the html head:

<meta name="viewport" content="width=device-width, user-scalable=no, target-densitydpi=device-dpi">

and the game images become very blurry. If I set the width to a certain value, it looks fine. I don’t know why! But I have to set it to device-width because I need to adapt the whole web page to mobile devices. Who can help me with this, I would be very appreciated?
This is the topic I posted not long ago, seems no one has an answer: The images are very blurry in my game.

It’s probably related to your device and the browser you test, can you give us more informations?

And what resolution policy/size are you using ?