Why Exclation mark beside network signal..?

[Vishnu Vardhan7]

Since my phone got updated to lollipop 5.0.2 from kitkat I am noticing there's always an exclamation (!) mark beside the wifi sign above. why is that ? My wifi seems to work fine. I can access the internet so as google pages. Everything seems to be ok but why still this sign ?

 

[UJ95x]

Weird. That's supposed to be for when you can't connect to Google services. Does it show on every WiFi network or just some?