ROOT_FOLDER error

[eluser]taju.joseph[/eluser]
Hi all,
I dont know how silly this error is but i am having a lot of problems with this please help me out.

While retrieving Images from the DB I am getting this error.
A PHP Error was encountered

Severity: Notice

Message: Use of undefined constant ROOT_FOLDER - assumed 'ROOT_FOLDER'

Filename: helpers/resize_helper.php

Line Number: 36
no image

many thanks
Thank you