How to solve “Error: Apache shutdown unexpectedly”?

 I try to start my Apache server in the XAMPP Control Panel, but got this error,

13:41:14  [Apache]     Attempting to start Apache app...
13:41:14  [Apache]  Status change detected: running
13:41:14  [Apache]  Status change detected: stopped
13:41:14  [Apache]  Error: Apache shutdown unexpectedly.
13:41:14  [Apache]  This may be due to a blocked port, missing dependencies, 
13:41:14  [Apache]  improper privileges, a crash, or a shutdown by another method.
13:41:14  [Apache]  Press the Logs button to view error logs and check
13:41:14  [Apache]  the Windows Event Viewer for more clues
13:41:14  [Apache]  If you need more help, copy and post this
13:41:14  [Apache]  entire log window on the forums