Last week the Google Custom Search blog posted about a couple of Custom Search Engine updates. One of these is a change I have been asking about for a long time, and it's great to see it.
Now the keywords that you program in the Basics tab of the control panel have a stronger effect on results. In a sense, they allow you to assume a context. Here is the example they provided in their post:
Compare the results on this yoga search engine when looking for a "mat" with and without the keyword "yoga" -- with keywords:
The reason that this is a really important change is that users get set in the context of the site. When they are on a yoga site using a yoga search engine, they don't expect that they will have to type in "yoga mat". The data I have seen shows that they want to type in "mat".
Every time you force a user to redo something because of a mismatch between their expectations and what you provide, some of them lose interest in going further and leave. This is not a good thing, but now you can address it with Google Custom Search Engines.