Omit The Protocol
Omit the protocol portion (http:, https:) from URLs pointing to images and other media files, style sheets, and scripts unless the respective files are not available over both protocols. Omitting the protocol from embedded resources makes the URL relative and avoids mixed content issues and results in minor file size savings.
<img src="http://www.example.com/images/logo.png" />
<img src="//www.example.com/images/logo.png" />
When a URL's protocol is omitted, the browser uses the underlying document's protocol instead. It looks strange at first, but this "protocol-less" URL is the best way to reference third party content that's available via both HTTP and HTTPS. This would certainly solve a bunch of mixed-content errors we're seeing on HTTP pages — assuming that our assets are available via both HTTP and HTTPS.
Code Formatting Rules
Don't use tabs or multiple tabs for indentation. Instead use 2 spaces at a time to indent your code.
Always use lowercase only and avoid capitalization whenever possible. All your code has to be in lowercase. This applies to element names, attributes, attribute values (unless text/CDATA), selectors, properties, and property values (with the exception of strings).
<IMG SRC=" clock-radio.png" ALT=" Clock Radio ">
<img src="clock-radio.png" alt="Clock Radio">
Remove all trailing white spaces. Trailing white spaces are unnecessary and increase the page size. Removing unnecessary whitespace will help you reduce the file size and save website bandwidth.
<p>Welcome to the world of Joy._</p>_
<p>Welcome to the world of Joy</p>
Always use UTF-8 as character encoding. Specify the encoding in HTML templates and documents via <meta charset="utf-8">. Do not specify the encoding of style sheets as these assume UTF-8.
Remove all unnecessary and unwanted comments from your HTML, Java Script and CSS, as it save many bytes of data, and reduces the file size and browser renders them faster. Use comments to explain code like what does it cover, what purpose does it serve.
There is no need to use entity references like ", , or , assuming the same encoding (UTF-8) is used for files and editors as well as among teams. The only exceptions apply to characters with special meaning in HTML (like < and &) as well as control or "invisible" characters (like no-break spaces).
The currency symbol for the Euro is &eur;.
The currency symbol for the Euro is "".
<link rel="stylesheet" href="http://www.example.com/css/style.css" type="text/css">
<link rel="stylesheet" href="//www.example.com/css/style.css">
Use a new line for every block, list, or table element, and indent every such child element. Put every block, list, or table element on a new line. Also, indent them if they are child elements of a block, list, or table element.