Title: How can I search my journal? How do I find a particular entry or comment?
LiveJournal does not have a way of searching entries in a journal. However, the month view of a journal (http://www.livejournal.com/users/exampleusername/yyyy/mm/) will display all entries made in that journal in that month, listing them by date/time and by the subject line of the entry. (For community entries, it will also display the username of the person who posted the entry.) If you remember the subject line used for the entry you are searching for, you can use this method to find the entry.
If you remember the approximate date of the entry you are looking for, you can use the Day view of the journal (http://www.livejournal.com/users/exampleusername/yyyy/mm/dd/) to view all entries made on that day. Most styles provide a way of going to the next or previous day.
Both of these views can also be accessed through the Calendar or Archive for that journal.
It is possible to search public entries in a journal by using Feedster. This is an external service that is not affiliated with LiveJournal, but as a convenience, LiveJournal does provide a search interface for searching a journal using Feedster. This interface can be accessed at http://www.livejournal.com/tools/search.bml?journal=exampleusername, or by clicking on the magnifying glass icon on the userinfo page for that user. (Feedster will only search through public entries, and so will not find information in a private or protected entry.)
Before you can use Feedster to search through a journal, that journal's RSS feed (http://www.livejournal.com/users/exampleusername/data/rss) may need be added to Feedster. For further details, please refer to the documentation and support available on the Feedster website (http://www.feedster.com).
Please note that Feedster is not affiliated with LiveJournal, and so LiveJournal is not responsible for the resulting content or for any changes in availability that may occur.
When you are logged in, your Recent Comments page (http://www.livejournal.com/tools/recent_comments.bml) will display the most recent comments that you have received and posted. (Please note that the comments received will only include comments that were posted to your journal, and will not include comments you receive to community entries, or responses to comments you have left in other journals. The comments posted will include comments you have posted in any journal or community.) The number of comments displayed on this page depends on your account type.
Aside from this page, LiveJournal does not provide any method of displaying comments that you have received, or of searching through a journal to find a particular comment. If you remember what entry it was a comment to, you can use the instructions above to locate the entry in question, and then view the Read Comments page for that entry. You can also navigate through entries. (Please note that if comments have been disabled on the journal or on that specific entry, existing comments will not display.)
If you have chosen to receive comment notification emails (http://www.livejournal.com/support/faqbrowse.bml?faqid=62), and save the emails that you receive, you may be able to find a particular comment using these emails, using a 'search' function in the program you use to read email. For information on whether or not your email client allows you to search through messages, please consult the documentation for the program. (Please note that LiveJournal cannot provide instructions for doing this, or guarantee that this method will work.)
FURTHER READING, which I'm too lazy to actually linkify
* RSS feed
* paid account and/or paid account benefits, for the Recent Comments thing? or not. probably not.
[and yes, I know the comment-finding info is kind of duplicated in faq 62. or rather, I'd forgotten, and I wrote this offline, and then I went online and kind of went oops. though maybe the bit in 62 could be moved over here, if this FAQ gets adopted, and then 62 could just say "please see blah for information on finding comments" and then have information on how to read them. Or something.]