A flash of unstyled happy ( FOUC , aussi flash of unstyled text or FOUT )   is an instance WHERE a webpage Appears Briefly with the browser’s default styles prior to loading an external CSS stylesheet , due to the web browser engine rendering the page before all information is retrieved. The page is correct and the rules are loaded and applied; however, the shift may be distracting. Related problems include flash of invisible text (FOIT) and flash of false text (FOFT).  
The issue has been documented in an article named “Flash of Unstyled Content”.  At first, FOUC Appeared to be a single problem browser to Internet Explorer purpose est devenu apparent later in other browsers,   and since beens HAS Described as “a Safari epidemic”. 
FOUC is indifferent to changes in CSS or HTML versions. The problem originates from a set of priorities in the browser. [ citation needed ] As the browser collects the Document Object Model on-the-fly. The browser can choose from the text, which it can parse the quickest.
FOUC is more prevalent than HTML pages. Web pages often include style references to media other than the browser screen, such as CSS rules for printers and mobile devices. Web pages can import layers of style files and reference alternative style sheets. Online advertisements and other inserts, their own style and their rules. The cascading nature of the CSS rules encourages some browsers to wait until it is collected.
To emulate an FOUC, developers can use browser add-ons that are capable of disabling a webpage’s CSS on-the-fly. Firebug is one such add-on.
- ^ Jump up to:a b c Tim Brown (3 June 2016). “Looking at the Flash of Unstyled Text in Chrome 50” . Adobe Typekit blog . Adobe Systems . Retrieved 9 August 2016 .
- ^ Jump up to:a b c Chris Coyier (1 April 2015). “FOUT, FOIT, FOFT” . CSS Tricks . Retrieved 9 August 2016 .
- Jump up^ “Flash of Unstyled Content (FOUC)” . Blue Robot. 2001. Archived from the original on May 13, 2015 . Retrieved 12 October 2012 .
- Jump up^ “Flash of Unstyled Content (FOUC)” . Bugzilla @ Mozilla . Retrieved 14 October 2016 .
- Jump up^ “Chromium Bugs containing ‘FOUC ‘ ” . bugs.chromium.org . Retrieved 14 October 2016 .
- Jump up^ Dave Hyatt (September 1, 2006). “The FOUC Problem” . Surfin ‘Safari . The WebKit Open Source Project . Retrieved 16 October 2012 .
The FOUC problem would normally be a minor occurrence. However with the advent of Google AdSense , FOUC has become an epidemic safari . Because these things are often not done in the same way as they do in the page, the problem is so much more severe than it should be.
- Jump up^ Bram Stein (28 July 2016). “Changes to web font serving on Typekit” . Adobe Typekit blog . Adobe Systems . Retrieved 9 August 2016 .