The most common attributes are as follows...

Attribute NameElementsDescription
align<applet> , <caption> , <col> ,<colgroup> ,  <hr> , <iframe><img> , <table> , <tbody> , <td> ,  <tfoot> , <th> ,<thead> , <tr>Specifies the horizontal alignment of the element.
alt Alternative text in case an image can't be displayed.
autoplay<audio> , <video>The audio or video should play as soon as possible.
bgcolor<body> , <col> , <colgroup> ,<marquee> , <table> , <tbody><tfoot> , <td> , <th> , <tr>
Background color of the element.
Note: This is a legacy attribute. Please use the CSS background-color property instead.
border<img> , <object> , <table>
The border width.
Note: This is a legacy attribute. Please use the CSS border property instead.
checked<command> , <input>Indicates whether the element should be checked on page load.
cite<blockquote> , <del> , <ins> ,<q>Contains a URI which points to the source of the quote or change.
classGlobal attributeOften used with CSS to style elements with common properties.
code<applet>Specifies the URL of the applet's class file to be loaded and executed.
color<basefont> , <font> , <hr>
This attribute sets the text color using either a named color or a color specified in the hexadecimal #RRGGBB format.
Note: This is a legacy attribute. Please use the CSS color property instead.
cols<textarea>Defines the number of columns in a textarea.
colspan<td> , <th>The colspan attribute defines the number of columns a cell should span.
content<meta>A value associated with http-equiv or namedepending on the context.
dirGlobal attributeDefines the text direction. Allowed values are ltr (Left-To-Right) or rtl (Right-To-Left)
dirname<input> , <textarea>
disabled<button> , <command> ,<fieldset> , <input> ,<keygen> , <optgroup> ,<option> , <select> ,<textarea>Indicates whether the user can interact with the element.
form<button> , <fieldset> ,<input> , <keygen> , <label> ,<meter> , <object> , <output><progress> , <select> ,<textarea>Indicates the form that is the owner of the element.
headers<td> , <th>IDs of the <th> elements which applies to this element.
height<canvas> , <embed> , <iframe><img> , <input> , <object> ,<video>Note: In some instances, such as <div> , this is a legacy attribute, in which case the CSS height property should be used instead. In other cases, such as <canvas> , the height must be specified with this attribute.
href<a> , <area> , <base> , <link> The URL of a linked resource.
hreflang<a> , <area> , <link>Specifies the language of the linked resource.
list<input>Identifies a list of pre-defined options to suggest to the user.
loop<audio> , <bgsound> ,<marquee> , <video>Indicates whether the media should start playing from the start when it's finished.
low<meter>Indicates the upper bound of the lower range.
manifest<html>Specifies the URL of the document's cache manifest.
max<input> , <meter> ,<progress>Indicates the maximum value allowed.
maxlength<input> , <textarea>Defines the maximum number of characters allowed in the element.
media<a> , <area> , <link> ,<source> , <style>Specifies a hint of the media for which the linked resource was designed.
method<form>Defines which HTTP method to use when submitting the form. Can be GET (default) or POST.
min<input> , <meter>Indicates the minimum value allowed.
multiple<input> , <select>Indicates whether multiple values can be entered in an input of the type email or file.
name<button> , <form> ,<fieldset> , <iframe> ,<input> , <keygen> , <object><output> , <select> ,<textarea> , <map> , <meta> ,<param>Name of the element. For example used by the server to identify the fields in form submits.
placeholder<input> , <textarea>Provides a hint to the user of what can be entered in the field.
poster<video>A URL indicating a poster frame to show until the user plays or seeks.
rel<a> , <area> , <link>Specifies the relationship of the target object to the link object.
required<input> , <select> ,<textarea>Indicates whether this element is required to fill out or not.
reversed<ol>Indicates whether the list should be displayed in a descending order instead of a ascending.
rows<textarea>Defines the number of rows in a textarea.
rowspan<td> , <th>Defines the number of rows a table cell should span over.
selected<option>Defines a value which will be selected on page load.
size<input> , <select>Defines the width of the element (in pixels). If the element's type attribute is text orpassword then it's the number of characters.
span<col> , <colgroup>
src<audio> , <embed> , <iframe> ,<img> , <input> , <script> ,<source> , <track> , <video>The URL of the embeddable content.
styleGlobal attributeDefines CSS styles which will override styles previously set.
tabindexGlobal attributeOverrides the browser's default tab order and follows the one specified instead.
titleGlobal attributeText to be displayed in a tooltip when hovering over the element.
type<button> , <input> ,<command> , <embed> ,<object> , <script> ,<source> , <style> , <menu>Defines the type of the element.
value<button> , <option> , <input><li> , <meter> , <progress> ,<param>Defines a default value which will be displayed in the element on page load.
width<canvas> , <embed> , <iframe><img> , <input> , <object> ,<video>Note: In some instances, such as <div> , this is a legacy attribute, in which case the CSS width property should be used instead. In other cases, such as <canvas> , the width must be specified with this attribute.

*thanks to Mozilla Developer Network for the attribute list

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