Here are few points to helps you better understand the similarities and differences among older versions of HTML, XHTML and the latest HTML5:
All versions of HTML include tags that are designed to the hierarchical. Examples are the <h1>(heading 1) to <h6>(heading 6) tags. Reserve the <h1> tag for the most important text on the page, such as the top headline. The <h2> tag is ideal for subheads or secondary headings , <h3> for the third level of headings, and so on. A headlines formatted with the <h1> tag looks like this:
HTML5 adds new tags . HTML5 adds a collection of tags designed to make webpages more semantic, or more meaningful. New tags, including <header> and <footer>, can be used to identify the type of content in a webpage.
XHTML tags must be written in lowercase. HTML5 and older versions of HTML are not case sensitive.
In XHTML, all tags must be include the closing slash. A few tags can stand alone, such as the <br/> tag, even if there’s only one tag, and the close tag must always contain a forward slash (/). Thus the line break tag is <br> in HTML and <br/> in XHTML.
At their heart, all versions of HTML are just text – and believe it or not, you can write HTML in plain text editor as simple as Notepad, SimpleText, or TextEdit. However, you have to be careful to type all the code perfectly because there is no room for error or typos in HTML. After writing code yourself, even to create a simple page, you’re sure to appreciate how wonderful it is to let Dreamweaver write the code for you.
If (all the first glance) you think that HTML code looks like hieroglyphics, you can start to recognize at least the most common tags, such as <h1> (heading 1) tag used to format the headline.