The markup tags in Visualforce correspond to various parts of the Force.com GUI. These tags allow you to quickly generate HTML markup without actually writing any HTML. It's really one of the greatest tricks of the Salesforce1 Platform. You can easily create your own custom screens that look just like the built-in ones with less effort than it would take you to create a web page for your corporate website. Take a look at the Visualforce markup that corresponds to the HTML and screenshot we showed you earlier:

<apex:page standardController="Account" >
  <apex:sectionHeader title="Account Edit" subtitle="New Account" />
  <apex:form>
    <apex:pageBlock title="Account Edit" mode="edit" >
      <apex:pageBlockButtons>
        <apex:commandButton value="Save" action="{!save}" />
        <apex:commandButton value="Cancel" action="{!cancel}" />
      </apex:pageBlockButtons>
      <apex:pageBlockSection title="Account...