How to bold words in more tag

I’m trying to make the more tag text bold, and maybe change what it says. The only reference I can find is in the index file:

<?php the_content(‘Continue’); ?>

The Style Sheet doesn’t include anything I can recognize as controlling the “more” text. I don’t know enough about PHP to figure out if I can just add something to that line to make the word Continue bold, and if I can use more than one word in place of Continue.

And, I’m afraid to just try something because the last time I did that the results got me into a huge mess.

Any help would be appreciated.