I own a corporation and I stopped signing confidentiality agreements years ago. If I sign an agreement in regard to something we're already working on it opens us up to risk if someone we've never met, whose idea we've never seen, suddenly interferes with our rights to our own ideas.
Serious investors generally don't sign confidentiality agreements. If they did, they'd rule out a whole class of ventures for having looked at one, whether they liked that one or not. Almost every attorney you ask will tell you that you have to have a confidentiality agreement without caring a bit about the fact that most serious people and companies won't sign them because it cuts their future freedom.
And yet another problem is that you can't "own" an idea. Patents protect inventions, copyright protects creative works, trademarks protect commercial words and images. Nothing legally protects an idea. You don't own it.
The only way you really protect an idea is to build a company, launch it, bring it to market and stake out your territory like an explorer planting a flag. You'll want to be so good and so fast that no larger company copies it and beats you at your own game. Copying is excruciatingly legal in our economy. Nothing protected Yahoo from Google, for example.
So what to do? The best thing is to build the website and own it yourself. If you need investment -- unless you really, really trust these people at the major corporation -- collect a team of experienced people and sell the idea and the team to implement it to angel investors. They don't want to steal your idea because you have the team to implement it, and they don't.
Related: Find the Right Person to Protect Your Idea
Related: How to Find the Right Investor for Your Business