Joomla 2.5 has reached its end of life as for 12/31/2014. Please be advised this may be a security risk to your website. You can view more information about the end of life here.
Strikethrough text is often used to show corrections / changes within an article, while at the same time still showing the original text. For example, this text here shows how strikethrough text appears. The Joomla 2.5 article editor makes it very easy to update your article and use strikethrough text.