function isEmpty(s){return (s.length==0)}
function isNum(n){return /^-*[\d]+\.*[\d]*$/.test(n)}
function isInt(n){return /^-*[\d]+$/.test(n)}
function isDate(d,m,y){return (isInt(d)&&isInt(m)&&isInt(y))&&!((d<1||d>31||m<1||m>12)||(d==31&&(m==2||m==4||m==6||m==9||m==11))||(d==30&&m==2)||(d==29&&m==2&&(y%4!=0||(y%100==0&&y%400!=0))))}
function isEmail(s){return /^[\w\.-]+\@[\w\.-]+\.[\w]+$/.test(s)}
function hasLength(s,m,M){return (s.length>=m&&s.length<=M);}
function warn(f,m){alert(m);f.focus();return false;}