16x2 Display shows characters with white squares

Hi i don't know what's wrong but my 16x2 does not work well, the characters are displaying but it has white squares with it so i can't see the texts clearly.

This is the one i'm using and i followed the tutorial on this site
http://henrysbench.capnfatz.com/henrys-bench/arduino-displays/ywrobot-lcm1602-iic-v1-lcd-arduino-tutorial/

Anyone has encountered the same?

Maybe high contrast of display.

Adjust the contrast potentiometer. The link you provided in your original post has a picture showing where to find it.

Don