It all depends on the kind of person you are as to whether this sort of stuff will work or not.
In my personal experience, getting people to keep food diaries, and buy into the idea of going on a 'diet' for a concentrated period of time does not help in relation to them making long term fat loss and lifestyle changes.
Right now, what I absolutely dont want you to do is think of an eyeball.
You just thought of one didnt you? Couldnt help it.
Food diaries are like this. All the time you are writing it, preparing to write it, taking it with you etc. you are concentrating on food, what you are eating, what you are not eating. This can easily lead to an existence revolving around your nutrition. A Mildly obsessive state that leaves little room for focus on other things. Thats not healthy.
Much of the time, poor eating habits are symptomatic of other life issues- stress, depression, comfort, rebellion, whatever. A food monitoring site will do nothing to address psychological triggers to poor diet, and so will be of little value.
Healthy eating does not require an awful lot of thought, its not a difficult thing to do. Lots of fruit and veg, plenty of water, low salt, little red meat and full fat dairy, low alcohol, sensible portions at sensible times of the day. There it is. 1 paragraph to healthy eating.
The difficulty arises in creating a mindset where the above is not seen as boring, and some sort of punishment, but as a positive and desireable way of life. A website wont do that for you.