I am getting this error while a contract compilation using online solidity compiler :<br/><br/> `Untitled:23:19: Error: Member "value" not found or not visible after argument-dependent lookup in string storage pointer - did you forget the "payable" modifier?
	    var amount = msg.value;
	                 ^-------^` <br/><br/> Contract code is like this : <br/><br/>`function transfer(address user) payable {
	    var amount = msg.value;
		var sender = msg.sender;`<br/><br/>What wrong i am doing ?