The 2 best solutions:
- Google Custom Search (GCS)
- SQL Server (manual)
GCS:
Here you will rely totally on Google. If they index your webpage in 60 days, then good luck. You won't find info which isn't stored, publically like a webpage. Therefore, any content within the login, forget it.
You will also rely on Search Engine Optimization. if you don't optimize your page titles, meta descriptions ect, the search won't be of much use.
Custom SQL Server:
If you put a full text index on your data fields, you can search for your keywords. This is a decent solution, but remember the indexes (otherwise it will be very slow).
I would search for "SQL Server Full text search" for help on this solution.
The benefit here is you have full control and you can access everything.
EDIT:
There are of course many other solutions. I would also suggest looking into Lucene, or some implementations on top of Lucene such as Solr. However all search functionality is usually very difficult and timeconsuming, henceforth my first two suggestions.
In the company I work at we've previously used FAST, and use Apptus today.
EDIT 2:
Today I would advice one solution only: ElasticSearch. It's a great solution; easy to work with; works on all platforms; based on a nice REST api and JSON and is performing very well.