From http://www.w3schools.com (Copyright Refsnes Data)

HTML <tt> <i> <b> <big> <small> tags

Example

Format text in a document:

<tt>Teletype text</tt>
<i>Italic text</i>
<b>Bold text</b>
<big>Big text</big>
<small>Small text</small>

Try it yourself!

Definition and Usage

The <tt>, <i>, <b>, <big>, and <small> tags are all font-style tags. They are not deprecated, but it is possible to achieve richer effect with CSS.

<tt> Renders as teletype or mono-spaced text
<i> Renders as italic text
<b> Renders as bold text
<big> Renders as bigger text
<small> Renders as smaller text

Browser Support

Internet Explorer Firefox Opera Google Chrome Safari

The <tt>, <i>, <b>, <big>, and <small> tags are supported in all major browsers.

Differences Between HTML and XHTML

NONE

Standard Attributes

id, class, title, style, dir, lang

For a full description, go to Standard Attributes.

Event Attributes

onclick, ondblclick, onmousedown, onmouseup, onmouseover, onmousemove, onmouseout, onkeypress, onkeydown onkeyup

For a full description, go to Event Attributes.

From http://www.w3schools.com (Copyright Refsnes Data)