Do you have the problem that when you Search, you can’t find it? Check the Search Tips, a sticky at the top of About BOB about How To Search,.
Also be aware that there are words that are excluded from the Search Database. That sticky has a second posting, which discusses Stop Words which are excluded from the Search Database.
For your reference you may review the list of prohibited search terms by looking at the stop words list (link removed).
Bobarella (BOB member since 2004-02-12)
Let me supplement the previous post with an explanation for “why” some of the words appear on the stop words list. Without getting into too much detail, each word that appears in each post is indexed. Certain words, as you might expect, are very common on this site. For example, the word “universe” was found in around 20% of the posts on this site the last time I checked. As such it was not a very good search term. Who wants to read 20% of 200K posts? 
Not only is it not a very good search term, but any word that appears in more than 20% of the posts on the system places a huge strain on the server when it is used as a search term.
In order to avoid this, the stop words are dropped from your search terms. They are dropped “silently” meaning that you don’t get informed of the process, which is something that we can address. But that’s why you sometimes don’t find results for words that you know are there.
Dave Rathbun 
(BOB member since 2002-06-06)
I agree these Stop words are useless by themselves but they can come in very handy while combined with other terms. Is there any way around this, for when you explicitly want to use one of the stop words in your search?
EJ972813 (BOB member since 2006-11-22)
One alternative is to use the Google Search that is at the bottom of each page in place of the BOB Search – perhaps you can then find the exact phrase for which you seek.
Bobarella (BOB member since 2004-02-12)