LCD displays are made of glass, so there are several ways for them to crack.
If the lines are either in spider web form or are in a non-symmetrical form much like a broken window, it is a cracked screen. Straight/symmetric lines are atypical of a broken piece of glass.
Additionally, with the computer turned off, you can usually hold the LCD at an angle that directly reflects a light source (just like holding a mirror in a way that the light hits your face) and see the same cracks. If you see the same lines with the computer turned off that you see with the computer on, it is cracked. See the graphics below for visual examples.
Cracked LCD displays are not covered under the normal warranties and should be serviced through our out-of-warranty process.
This document contains a few examples of cracked LCD panels.
If you would like assistance with out of warranty service for the LCD panel on your Acer notebook computer, please contact Acer support.