You can provide a gadget to do a direct blog search, in addition to the search gadget in the Navbar - or (if you block the Navbar), you can do this instead of the search gadget in the Navbar.
But what if you have multiple blogs, maybe in a custom domain cluster, that you want your reader to search in combination? Or maybe you would like refinements to your search? That's when you use the Google Custom Search Engine.
The Custom Search Engin gives you lots of choices - from scope (one blog, many blogs), to display options (appearance of the search box, and of the search results, are both customisable) - and refinements (where you can merge searches from outside sites with your sites, and prioritise your sites).
There are advantages to both choices.
- The direct search gadget is simple, with no options required (except the caption for the button), and provides the search results as an index page in the blog (very user friendly)..
- The Google CSE gadget is very versatile, with lots of settings - and it provides the search results in a Search Engine Results Page format.
The most relevant difference, in my opinion, is the source for the searches.
- The direct search targets one single blog directly, and dynamically. Whatever changes you made to the blog 5 minutes ago will be included in the search. A direct search produces good result for private blogs.
- The Google CSE targets the Google Search Engine cache. The CSE will have results only as current as what GoogleBot found during its last pass through each web site included in the search - and works best for blogs visible to everybody, and properly publicised.
- Blogger blogs are indexed, by the search engines, from the blog posts newsfeed. Since private blogs don't publish a newsfeed, they won't be indexed, and won't produce results in the CSE.
A third alternative would be a Google Custom Search "Search Box" gadget, which you add using the "Add a gadget" wizard in the dashboard Layout wizard. Slightly less versatile than a Google Custom Search, the "Search Box" gadget combines blog searches and web searches, into a comprehensive and configurable multi tab search.
- Search this blog.
- Search websites linked in the blog posts.
- Search websites linked in the bloglists and linklists.
- Search the web.
It all depends upon what you think will serve your readers best. But consider the several choices, carefully.