JDocumentHTML in 'Basic Settings'

I upgraded from Joomla 1.7.5 to 2.5.1, and appeared the following error:
JDocumentHTML
JDocumentHTML
in 'Basic Settings'

(see attachment)


Using Gk coffee Template Version: 2.5 Date: 07/12/2011 upgradarlo and I can not upgrade it because I changed some css files.
I ask:
1-is a serious problem?
2-how can I solve this problem without upgrading the template?
thanks

You probably upgrade only Joomla! not template, please download latest version from our download section and overwrite all files via ftp connection.

bkrztuk,
Yes I have upgraded Joomla from 1.75 to 2.5.1. The Coffee template is a Version 2.5.
I changed some files to optimize the template for my purpose, and if I make an update to version 2.5.1 of Cofee template these files are replaced.
I ask if I can replace via FTP only the files mentioned in the file 'changes' of the template version 2.5.1:

Changed files:<br /><br />
- templateDetails.xml<br />
- admin/scripts.js<br />
- html/com_content/article/default.php<br />
- html/com_content/category/blog_item.php<br />
- html/com_content/featured/default_item.php<br />
- js/gk.scripts.js<br />
- js/ie7.equal.columns.js<br />
- js/menu.gkdropline.js<br />
- js/menu.gkmenu.js<br />
- lib/gk.const.php<br />
- lib/gk.framework.php<br />

Thank you for your help and sorry for my language