The content plugin allows you to manipulate Joomla's article content before they are displayed.
When in a content plugin in Joomla, the article is represented by the object $row in Joomla 1.0. This $row is the result of a database query for the article, and thus contains the article title in $row->title, the article text in $row->text etc.
To modify the text of an artile in Joomla 1.0 we have to modify $row->text.
Example:
We want to add a horizontal line after every article. A horizontal line is <br />
<?php
$row->text .= '<br />';
?>
Thats it. Notice the dot before the = sign. (.=). This appends to the string.