If you have been using Android 5.0 Lollipop for some time now you might have noticed a small exclamation mark next to WIFI signal. Google has made Android 5.0 a little smarter when it comes to choosing a connection, if it detects it is connected to a WIFI that doesn’t have an internet connection it will automatically switch to 3G to keep the connection going, if this is the case your device will show an icon similar to the one in the image bellow:
This is pretty cool and handy, specially for those who don’t have great internet at home. Previous Android versions would simply show a modified icon of which many users had no clue what it meant and weren’t sure what to do to fix it. The Wifi icon with the Exclamation mark will also appear on notification center if there is no connection.
While you are at it, you might also find it interesting to compare your Wifi and 3G/4G speed, learn how to do so here