1.html的头文件
2.写兼容模式
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="https://www.w3.org/1999/xhtml" xml:lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <meta http-equiv="Pragma" content="no-cache"> <meta http-equiv="Cache-Control" content="no-cache"> <meta http-equiv="X-UA-Compatible" content="IE=edge" /> <meta http-equiv="Expires" content="0"><!DOCTYPE html PUBLIC
