Limit excerpt in Archive page

There is no reliable way of limiting the_content without stripping all tags. try it with putting the <!--more--> tag where you want the post to stop. And set the the $more variable to -1, on loops where you don’t want to have the “read more” link on the content: http://codex.wordpress.org/Customizing_the_Read_More#More_about_.24more

Or use manual excerpts with the_excerpt() to show the posts on the archive pages. A manual excerpt doesn’t get stripped of al its tags.