function check_mail(){

	var error = false;
		
		
		document.user_form.vorname.style.background = "white";
		document.user_form.name.style.background = "white";
		document.user_form.anschrift.style.background = "white";
		document.user_form.plz.style.background = "white";
		document.user_form.ort.style.background = "white";
		document.user_form.abs_mail.style.background = "white";
		
				
		
		if(document.user_form.name.value == ""){
			document.user_form.name.style.background = "red";
			error = true;
		}
		if(document.user_form.vorname.value == ""){
			document.user_form.vorname.style.background = "red";
			error = true;
		}
		/*
		if(document.user_form.anschrift.value == ""){
			document.user_form.anschrift.style.background = "red";
			error = true;
		}
		if(document.user_form.plz.value == ""){
			document.user_form.plz.style.background = "red";
			error = true;
		}
		if(document.user_form.ort.value == ""){
			document.user_form.ort.style.background = "red";
			error = true;
		}
		*/
		if(document.user_form.abs_mail.value == "" || document.user_form.abs_mail.value.indexOf("@") == -1){
			document.user_form.abs_mail.style.background = "red";
			error = true;
		}
		
		
				
				
		if(error) {
			alert("Sie haben wichtige Felder ausgelassen!");
			return false;
		}else return true;
}