The HTML <source> element specifies multiple media resources for either the <picture>, the <audio> or the <video> element. It is an empty element. It is commonly used to serve the same media content in multiple formats supported by different browsers.
The HTML Subscript Element (<sub>) defines a span of text that should be displayed, for typographic reasons, lower, and often smaller, than the main span of text.
The HTML Superscript Element (<sup>) defines a span of text that should be displayed, for typographic reasons, higher, and often smaller, than the main span of text.
The HTML Table Element (<table>) represents tabular data - i.e., information expressed via a two dimensional data table.
The HTML Table Body Element (<tbody>) defines one or more <tr> element data-rows to be the body of its parent <table> element (as long as no <tr> elements are immediate children of that table element.)  In conjunction with a preceding <thead> and/or <tfoot> element, <tbody> provides additional semantic information for devices such as printers and displays. Of the parent table's child elements, <tbody> represents the content which, when longer than a page, will most likely differ for each page printed; while the content of <thead> and <tfoot> will be the same or similar for each page printed. For displays, <tbody> will enable separate scrolling of the <thead>, <tfoot>, and <caption> elements of the same parent <table> element.  Note that unlike the <thead>, <tfoot>, and <caption> elements however, multiple <tbody> elements are permitted (if consecutive), allowing the data-rows in long tables to be divided into different sections, each separately formatted as needed.
The Table cell HTML element (<td>) defines a cell of a table that contains data. It participates in the table model.
The HTML Table Foot Element (<tfoot>) defines a set of rows summarizing the columns of the table.
The HTML element table header cell <th> defines a cell as header of a group of table cells. The exact nature of this group is defined by the scope and headers attributes.
The HTML Table Head Element (<thead>) defines a set of rows defining the head of the columns of the table.
The HTML element table row <tr> defines a row of cells in a table. Those can be a mix of <td> and <th> elements.
The HTML Underline Element (<u>) renders text with an underline, a line under the baseline of its content.
The HTML Variable Element (<var>) represents a variable in a mathematical expression or a programming context.
The HTML element word break opportunity <wbr> represents a position within text where the browser may optionally break a line, though its line-breaking rules would not otherwise create a break at that location.
The HTML5 specification brings several new elements to web developers allowing them to describe the structure of a web document with standard semantics. This document describes these elements and how to use them to define the desired outline for any document.
At first sight a <canvas> looks like the <img> element, with the only clear difference being that it doesn't have the src and alt attributes. Indeed, the <canvas> element has only two attributes, width and height. These are both optional and can also be set using DOM properties. When no width and height attributes are specified, the canvas will initially be 300 pixels wide and 150 pixels high. The element can be sized arbitrarily by CSS, but during rendering the image is scaled to fit its layout size: if the CSS sizing doesn't respect the ratio of the initial canvas, it will appear distorted.
Importing images into a canvas is basically a two step process:
An event handler for close events sent to the window. (Not available with Firefox 2 or Safari)
The ondblclick property returns the onDblClick event handler code on the current element.
An event handler for the error event. Error events are fired at various targets for different kinds of errors:
The onfocus property returns the onFocus event handler code on the current element.