What does the exclamation mark next to my wifi signal mean?

[Android Central Question]

I have a Android HTC desire 526, and when I'm at home for some reason I get the Wi-Fi signal with exclamation mark beside it up in the top left corner of my phone. And when it does this sometimes it lasts a min or two or sometimes it's a second and then gone and then right back to it then gone again. And how do I get it to stop.

 

[chanchan05]

It means that it's connected to the wifi but there is no internet connection, just local network