An error with our URL rewrite rules caused some pages to be not found (404 errors) when Google crawled our site.
I regularly watch for errors and fix database or coding issues when they arise. We usually avoid them altogether, but sometimes we're surprised to find a 404 and we fix it.
How bad is it? Supposing our goal is to establish "trust" and "authority" and keep the spider coming back for more pages, does anyone know how the spider acts programatically with crawl errors. Is there a point where the crawl frequency is reduced, or the SERPs affected?