字幕表 動画を再生する 英語字幕をプリント Every document should begin with a reference to a Document Type Definition (DTD). This definition declares which version of the HTML standard that the document follows. All browsers have default definitions so we don't have to declare one, but to be standard compliant it's recommended. The three versions defined are: strict, transitional, and frameset. The strict definition includes only the structural markup and does not contain any deprecated elements or attributes. Instead it leaves formatting up to Cascading Style Sheets. The transitional definition on the other hand includes everything that is deprecated, and is intended to smooth the transition over to the strict definition. Then there's the frameset definition, which is used by frame documents. It contains the same elements as the transitional definition except that it includes the frameset elements. To include a definition we add the document type declaration, or doctype, to the top of the webpage. We also have corresponding versions for XHTML documents. All of these templates can be found in Dreamweaver when a new document is created. Another standard that we should follow is to include metadata in the document, using the meta header tag. The tag requires either the name or http-equivalent attribute, paired with the content attribute. The http-equiv attribute will cause the metadata to be sent as HTTP header information. The most importantly metadata is the document's file format and its character encoding. Note that for XHTML documents we use another MIME type and subtype than for HTML. Metadata can also be used to help search engines by provide a description of the document and a list of keywords relating to the content. We can also use the meta tag to automatically redirect the visitor to a new page after a specific number of seconds.