Finally I found the point of the problem.
When you are going to insert the article link by pushing button "Article" in tinyMCE editor, joomla displays modal-window to select the article.
In ver.250 updated from ver.173, "catid"infomation disappear from the html-source of article link because of changing of core program below.
joomla/administrator/composents/com_content/views/articles/tmpl/modal.php
--- ver.1.7.3 (line 91)
<td>
<a class="pointer" onclick="if (window.parent) window.parent.<?php echo $this->escape($function);?>('<?php echo $item->id; ?>', '<?php echo $this->escape(addslashes($item->title)); ?>', '<?php echo $this->escape($item->catid); ?>');">
<?php echo $this->escape($item->title); ?></a>
</td>
---
--- ver.2.5.2 (line 96)
<td>
<a class="pointer" onclick="if (window.parent) window.parent.<?php echo $this->escape($function);?>('<?php echo $item->id; ?>', '<?php echo $this->escape(addslashes($item->title)); ?>', '<?php echo $this->escape($item->catid); ?>', null, '<?php echo $this->escape(ContentHelperRoute::getArticleRoute($item->id)); ?>');">
<?php echo $this->escape($item->title); ?></a>
</td>
---
Stay default, ContentHelperRoute which is located in "joomla/compenents/com_content/helpers/route.php" doesn't return infomation of " catid=* ". Sometimes it causes 404 not found.
The created article link is displayed at frontend article, as below:
http://localhost/joomla/component/conte ... html?id=26I fixed the problem by adding ",$item->catid" to the ContenHelperRoute value as below:
--- After change ver.2.5.2 (line 96)
<td>
<a class="pointer" onclick="if (window.parent) window.parent.<?php echo $this->escape($function);?>('<?php echo $item->id; ?>', '<?php echo $this->escape(addslashes($item->title)); ?>', '<?php echo $this->escape($item->catid); ?>', null, '<?php echo $this->escape(ContentHelperRoute::getArticleRoute($item->id,$item->catid)); ?>');">
<?php echo $this->escape($item->title); ?></a>
</td>
---
The created article link is displayed at frontend article, SEO friendly, maybe without "Article" header as below:
http://localhost/joomla/books/forchild/ ... houte.htmlIf you would like to remove '26-'part, you need to create menu item of the single article.
It is another problem and you can find the topic related this searching the global question thread by the words "remove 'Articles' header".
I hope the core programing team create patch for this problem.
Since I am not good at English and the programing, I have little confidence.
--Maybe related thread
viewtopic.php?f=615&t=663176