...mmmm....
yes, but what do you want to search on this 'dynamic site' ?
Is the site database driven ? If so, what db ?
Is it XML driven ?
What data elements would you want people to be able to search upon ?
What kind of information does your site provide/store ?
What pages are currently available that the search results could link to ?
Do you want to build your own ASP search function, or do you want a 3rd party tool ?
If you want a 3rd party tool, how much are you willing to pay ?
Essentially, 'dynamic' infers that you store data somewhere and get/present it based on input values to a query. With this in mind, you would need to consider the above to determine how to search that data store - is it a single table/field or is it a range of data in disparate tables ?
If your data doesn't change too often then why not build an index page that links to all the possibilities (dynamically of course), and just 'site google' it once it has been indexed?
I may be wrong, but I don't think that there are many tools (if any) that search unknown databases/datasources directly and create a results page that links to a meaningful page - not without a fair bit of development/configuration and innevitably cost.
If you want real power then Google do an out of the box hardware solution which is pretty powerful and you can set it to index your dynamic site every day (public google doesn't do this because of the miriad websites on the net). This would still need you to have a link to the content you want to search on as part of your navigation.
Again, this may not be right if you want instantanseous and up to date results - for this it is probably best if you build your own search function.
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