How correct this file has been modified outside..?

[bobbyonline]

I'm using Dreamweaver on a Windows 8.1 Enterprise and Xampp 1.8.2-2 VC9. I am still a bit of a beginner. I was working on a Joomla CMS, and got the error message "This file has been modified outside of dreamweaver, do you want to reload it?" And I chose yes. So, it wiped my file clean. my joomla file(.css .php .html) is now empty.
Please help and explain me

i used:
Windows 8.1 Enterprise
Xampp 1.8.2-2 VC9

[Altrea]

How is that related to XAMPP?
XAMPP don't modifies any of your joomla files.