STYLEGUIDE by itself opens the MATLAB Programming Style Guide Wiki in the MATLAB web browser.
STYLEGUIDE SEARCHTERM1 SEARCHTERM2 SEARCHTERM3 ... searches the style guide wiki for any number of provided search terms and opens the search results page in the MATLAB web browser.
STYLEGUIDE uses similar syntax to the WEB function with the exception that it does not expect a URL. Rather, any number of search terms may be used. All other inputs and outputs for WEB work for STYLEGUIDE, e.g. [STAT, BROWSER, URL] = STYLEGUIDE(SEARCHTERM,'-NOTOOLBAR','-NEW').

Examples:
styleguide naming conventions
searches the style guide for "naming+conventions."

styleguide -browser
opens the style guide in the system web browser

[stat,h] = styleguide;
opens the style guide. Use close(h) to close the browser window.

The content is primarily from Richard Johnson's "MATLAB Programming Style Guidelines" (used with permission). Richard has since published a 2.0 version.