big problem – pages cannot be found

please advise. when i click on all my postings (teasers) i get a message that the page cannot be found. is all my work lost? or is it a matter of tweaking the code to re-link with the pages that still exists somewhere? last night i was working on creating an archive page rather than archive links on the sidebar. i must have done something dumb. because now i have next to nothing. my page is at https://thepanamapages.com

thanks in advance for any help