function validation(f) {

	if(f.name.value=="" || f.name.value==" ") {
		alert("Please give your name.");
		f.name.focus();
		return false;
	}

	//suppression des espaces avant et apres l'adresse email
	adresse=f.mel.value;
	while(adresse.charAt(0)==" ") {adresse=adresse.substring(1,adresse.length)}
	while(adresse.charAt(adresse.length-1)==" ") {adresse=adresse.substring(0,adresse.length-1)}

	f.mel.value=adresse;
		
	if(adresse=="") {
		alert("Please give your email address.");
		f.mel.focus();
		return false;
	}

	posArobace=adresse.indexOf("@");
	posPoint=adresse.indexOf(".",posArobace);
	pos1erPoint=adresse.indexOf(".");
	dernierCar=adresse.substring(adresse.length-1, adresse.length);
	premierCar=adresse.substring(0,1);
	escAdresse=escape(adresse);
	
	if(adresse.indexOf("+")>=0 || adresse.indexOf("/")>=0 || adresse.indexOf("*")>=0 || posArobace<=0 || posArobace==(adresse.length-1) || adresse.indexOf("@",(posArobace+1))>0 || posPoint<0 || adresse.substring((posPoint+1),(posPoint+2))=="." || adresse.substring((pos1erPoint+1),(pos1erPoint+2))=="." || adresse.substring((posArobace+1),(posArobace+2))=="." || adresse.substring((posArobace-1),(posArobace))=="." || dernierCar=="." || dernierCar=="-" || dernierCar=="_" || premierCar=="." || premierCar=="-" || premierCar=="_" || escAdresse.indexOf("%20")>=0)	{
		alert("Your email address is invalid.");
		f.mel.focus();
		return false;
	}
	
	if(f.word.value=="" || f.word.value==" ") {
		alert("What word do you want to define?");
		f.word.focus();
		return false;
	}
	
	if(f.definition.value=="" || f.definition.value==" ") {
		alert("You did not give any definition.");
		f.definition.focus();
		return false;
	}
	
	else {
		return true;
	}
}