the_excerpt and the_content in the post of wordpress cause error

I am using the latest wordpress version, even I have a problem with post which contain href link is to be text on call the_excerpt (link is not working) but when I replace the_content its working?

why and what’s the reason from excerpt to content….

its the sample code…..

<?php while ( have_posts() ) : the_post(); ?>
<?php the_author();?>
**<?php the_content(); ?>**

// the above the_content is display the href link normally but when I replace the_excerpt href link is not working in the post why and what’s the reason