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I think meta descriptions are important. They are your first chance to display a call to action to a customer and to get them to click through to your site.  Hence a poorly written one, truncated etc. is probably not as enticing as one within the 160 characters - that does not truncate. We have acted for several clients where we have optimized the MD and improved the CTR by .08% (ie less than 1%) but that has amounted to over 20,000 additional clicks on their site a year. Also I loved Rand's WBF which indirectly addresses the issue, but correlates with my view, though probably not as strong that dwell time is a significant factor on ranking. https://moz.com/blog/impact-of-queries-and-clicks-on-googles-rankings-whiteboard-friday On your questions directly:- Will it hurt your SEO? - Yes, two possible reasons 1/ you keyword stuff it. 2/ no-one clicks through because you have a bad MD On truncation - there are exceptions, but google generally does not if you fit within there pixel/character limit. My view - draft and implement your MD's properly... Hope that assists.

If you can write a regular expression to redirect only the old URLs to a new page, such as the home page, or closest category page - without redirecting every mistyped URL - then I would go ahead and do that. However, you do not want to redirect every mistyped URL because that would create a "soft 404" situation. As Chris Menke mentioned below, if you have already redirected all of the "top pages" the rest, which probably have little or no external link authority, can just go to a 404 page, and will eventually be removed from the index. You will want to pay close attention to the 404 reports for several months afterwards just to make sure that you haven't missed any URLs with significant external traffic or links. If you really wanted to put in the extra effort you could redirect any page that gets more than 5 visits a day/month (you choose the threshold), and any that have at least one external link. That's what I would do, personally. Also, if the category name is in the old URL you could make the "catch all" redirects go to the most appropriate category instead of all going to the home page. It all depends on what you have to work with. If they are truly nonsensical you will probably end up just letting all of the URLs with no traffic or links 404. Good luck!