That website is a great idea. I think that writing about your feelings is always a great thing. If anything, it lets you tell yourself how you are feeling.
Many times, you may end up writing in your journal, but it can be directed towards a loved one - this can also turn into a letter to give to them if you want them to know how you feel.
If you are ever afraid of someone finding it, you can always shred it afterwards. Much easier than writing in code

I believe that the act of writing down helps so much.
At least for me, writing things down really helps me focus on what is going through my head. It makes so much more sense after I write it down.