Back it up and do it again... just in case.
If you have ever deleted a file by mistake or someone else has moved and lost it then just imagine losing your website.
It's better to be safe than sorry. There can be lots of reasons for losing your site, the server crashing, being hacked, or even deleting the site by mistake (I am almost ashamed to admit this but... :)
It doesn't matter which event causes loss of your site, if your only copy is the live version then you are living dangerously.
I have about 3 versions of my site I can fall back on. I have the site on a development server at home which is an exact copy of the live site. If I lose my site for any reason it will only be down for the time it takes to re upload it.
I also make weekly back ups of the site including the database for the forum. The back ups are created on the server then downloaded but its just as easy to download the site to somewhere safe once a week. Somewhere safe is not on the server but on a different computer.
So if I do something stupid I can always roll back the site to 1 week ago. If I have just added a new guide or section to the site then I do a back up at that point and download it as well.
Lots of people complain to their hosts about losing sites but the responsibility should really be on your shoulders to make sure you are covered for most eventualities.
If you lose your site after reading this then you have no one to blame apart from yourself :)