Transform your code into a more standards-compliant mode for smaller files and lower maintenance costs.
Adopt strict XHTML for faster downloads and parsing.
Create well- formed documents, close all tags, and fully qualify and quote all attributes.
Use lowercase markup and text.
Embed style sheets on high-traffic pages and link to external files everywhere else.
Link to external scripts, and group , compress, and defer where possible.
Minimize fragment identifiers.
Validate your XHTML; use HTML Tidy to clean up your code.
For more information about XHTML, check out these books and web sites: