Please can someone help me, I think I've made such an enormous f-up it's not true

I was installing an SSL cert onto a friends zencart and in the ftp program I went to click 'refresh' on the configure.php file but hit delete I had a copy on my desktop which I put back but now it's not working, the homepage is messed up (all the other stuff is there but splattered all over the place) and there's a red band with a warning that says-

WARNING_CONFIG_FILE_WRITEABLE

I've checked the config file against my own one and apart from the obvious differences (www. names) everything is the same- what's happened??

Thanks on advance