Warning: Fail to move file! like image below: This error correlative to tmp folder in Joomla 3.x.
Tmp Folder safe to assume that this temporary folder is used for miscellaneous purposes, and the files stored in this folder are most likely deleted or moved to a more permanent location almost immediately after being put in the tmp folder.
The tmp folder is defined in file configuration.php at line:
public $tmp_path = '/home/hello_world/public_html/hellow_world/tmp';
Now we will fix error above by:
Login as admin, chose System-> Global Configuration-> Server-> Path to Temp Folder, enter the full path to your tmp folder and then click the Save button in the top left of the page.
By default it will be set to (path/to/joomla)/tmp . If the new temp folder does not exist, Joomla 3.0 will attempt to create it the next time it needs it.