Title tag is one of the most important factors in SEO. It is like a title of the book which gives search engine and people visiting your site a hint of what is inside. Full title modification can give a better ranking for a targeted keyword/s.
In Joomla, the format of the title is [Site Name - Title Tag] by default. You cannot edit that in Joomla administrator. The best solution for this is edit the HTML/PHP code in theme but this may not be applicable in all joomla theme.
Step 1:
Go to EXTENSIONS>TEMPLATE MANAGER the choose the theme that you are currently using.
Step 2:
Click the edit theme and find this PHP Code [?php echo $GLOBALS['mosConfig_sitename']?]
Step 3:
Delete that code and click save but be sure add closing tags before doing this.
