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

HTML 5 <th> tag

Definition and Usage

Defines a table header cell in a table. The text within the th element usually renders in bold.

Differences Between HTML 4.01 and HTML 5

The "bgcolor", "height", "width", and "nowrap" attributes were deprecated in HTML 4.01, and are no longer supported in HTML 5.

In HTML 5 only the "colspan", "rowspan" and the "scope" attributes are supported.

Example

Source Output
<table>
<tr>
<th>Header 1</th>
<th>Header 2</th>
</tr>
<tr>
<td>Cell A</td>
<td>Cell B</td>
</tr>
</table>
Header 1 Header 2
Cell A Cell B

Attributes

Attribute Value Description 4 5
abbr abbr_text Specifies an abbreviated version of the content in a cell 4  
align left
right
center
justify
char		 Specifies the horizontal alignment of cell content. Not supported. Use CSS instead. 4  
axis category_names Defines a name for a cell 4  
bgcolor rgb(x,x,x)
#xxxxxx
colorname		 Specifies the background color of the table cell. Not supported. Use CSS instead. 4  
char character Specifies which character to align text on. Not supported. Use CSS instead. 4  
charoff pixels
%  		 Specifies the alignment offset to the first character to align on. Not supported. Use CSS instead. 4  
colspan number Indicates the number of columns this cell should span 4 5
headers header_cells'_id A space-separated list of cell IDs that supply header information for the cell. This attribute allows text-only browsers to render the header information for a given cell 4  
height pixels Specifies the height of the table cell. Not supported. Use CSS instead. 4  
nowrap nowrap Whether to disable or enable automatic text wrapping in this cell. Not supported. Use CSS instead. 4  
rowspan number Indicates the number of rows this cell should span 4 5
scope col
colgroup
row
rowgroup		 Specifies if this cell provides header information for the rest of the row that contains it (row), or for the rest of the column (col), or for the rest of the row group that contains it (rowgroup), or for the rest of the column group that contains it 4 5
valign top
middle
bottom
baseline		 Specifies the vertical alignment of cell content. Not supported. Use CSS instead. 4  
width pixels
%		 Specifies the width of the table cell. Not supported. Use CSS instead. 4  

Standard Attributes

class, contenteditable, contextmenu, dir, draggable, id, irrelevant, lang, ref, registrationmark, tabindex, template, title

For a full description, go to Standard Attributes in HTML 5.

Event Attributes

onabort, onbeforeunload, onblur, onchange, onclick, oncontextmenu, ondblclick, ondrag, ondragend, ondragenter, ondragleave, ondragover, ondragstart, ondrop, onerror, onfocus, onkeydown, onkeypress, onkeyup, onload, onmessage, onmousedown, onmousemove, onmouseover, onmouseout, onmouseup, onmousewheel, onresize, onscroll, onselect, onsubmit, onunload

For a full description, go to Event Attributes in HTML 5.

Try-It-Yourself Demos

Tables
How to create tables in an HTML document.

Headings in a table
How to display table headers.

Empty cells
How to use "&nbsp;" to handle cells that have no content.

Table with a caption
A table with a caption.

Table cells that span more than one row/column
How to define table cells that span more than one row or one column.

Tags inside a table
How to display elements inside other elements.

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