The casual Friday concept   was one of the first signs that strict dress rules for offices were starting to relax. The principle of casual Fridays seems to have appeared around the 1950s. It was probably in response   to the changing attitudes towards workplaces. Over time, some offices have relaxed their dress rules even more by using a "business casual" dress rule. On casual Fridays, employees   may wear clothes which are considered to be "business casual", meaning they still obey certain standards  . Clothes must be clean and in good condition, with no spots. Men are generally allowed to wear casual trousers and bright-colored clothes, and in some offices they may be allowed to wear button-down shirts or polo shirts, with or without a tie. Women often wear neat skirts or dresses; casual trousers are common and generally allowed to wear, except in very formal workplaces. As a general rule, extremely casual clothes, like jeans, shorts, T-shirts, tank tops, and so on, are not encouraged on casual Fridays. Employees are still expected to make an effort to look professional, out of respect for their offices and their customers. Many people feel that casual Fridays are good for employees'mood because they encourage employees to express their individuality   and feel more comfortable in the offices. Others feel that business casual clothing and the concept of casual Fridays don't show respect for the workplaces. Casual Fridays are dealt with differently, depending on the industry and the nation. The technology industry, for example, is well known for casual clothes in general, while major financial companies still dislike casual clothes. We can learn from the passage that   _  .
the casual Friday concept has been out of fashion people were required to wear formal clothes in offices before casual Fridays concept appeared the casual Friday concept had appeared before the 1950s employees who wear formal clothes lack individuality