HTML需要注意的几个标签
1.placeholder，作为提示信息
input type = "text" name = "文本" placeholder="请输入文本"
2.required 不能为空
input type = "email" name = "邮件" placeholder="请输入邮件" required
3.patten 正则表达式,可以搜索常用的正则表达式来粘贴上去，
https://www.cnblogs.com/dreamingbaobei/p/9717234.html
input type = "enail" name = "邮箱" patten = "正则表达式"
3.表单的method，为get ,post。以及他们的区别
https://www.cnblogs.com/yinrw/p/10694735.html
https://www.cnblogs.com/miluluyo/p/11196672.html
