There are lots of ways that webmasters can assess the health of their websites using Google Webmaster Tools. One good tip is to use a text browser like Lynx to look at your site. That’s because most search crawlers “see” pretty much what Lynx does. If your site’s full up with JavaScript, cookies, and Flash, crawlers might have a hard time crawling your site.
It’s also a good idea to find out if your server supports the HTTP header “if-then-modified.” With it, your server can tell Google if your content has changed since the last crawl of the site, saving you bandwidth.
If you use the robots.txt file, you can tell crawlers which directories can be crawled, and which can’t. Google Webmaster Tools has a robots.txt analysis page that can help you determine if you’re using robots.txt correctly. That way you can prevent crawling of things like search results pages or automatically generated pages that aren’t going to add any value for users finding you via search engine.
Another great test of how healthy your site is (at least as far as Google is concerned) is how fast pages load. You can use the Page Speed tool as directed here to check.
