function c____() { s="" if(form1.username.value=='') { s="请输入用户名!\n"; } if(form1.password.value=='') { s=s+"请输入密码!"; } if(s!="") { alert(s); return false; } return true } document.write('
'); document.write('用户名:'); document.write(''); document.write(' 密码:'); document.write(''); document.write(' '); document.write(' '); document.write(' ' ); document.write('
');