Just like content pages in SharePoint sites, master pages include HTML formatting in order to position objects, such as navigation, and content on related content pages. However, in the case of a master page, the master page defines common HTML elements, including
<form> tags. Notice that if you create a blank ASPX page in SharePoint Designer, that page initially includes common HTML elements, including
<body> tags. When you subsequently attach a master page to that page, those sections are removed because the page then inherits HTML elements from the master page.
SharePoint 2010 master pages predominantly use DIVs and CSS to position and lay out objects and content. However, there are several table ...