How Do I Prevent Daily 404 (Not found) Errors to My WordPress BLog?

Hello,

I have been receiving 404 (Not found) Errors from my WordPress blog at internettvdotcom.com every day for many months. As a result of this, I have been constantly removing those urls using the webmaster tools. This is redundant and getting out of hand. I need to know how do I prevent all of these 404 errors from occurring.

Here are the type of urls showing 404 errors…

http://internettvdotcom.com/satellite-tv-for-pc-screenshots/
404 (Not found) 4 pages Dec 11, 2011

http://internettvdotcom.com/tag/is-dishnetpc-legitimate/
404 (Not found) 4 pages Dec 11, 2011

http://internettvdotcom.com/tag/satellite-tv-for-pc-keys/
404 (Not found) 6 pages Dec 11, 2011

http://internettvdotcom.com/tag/tv-on-pc-best-software/
404 (Not found) 6 pages Dec 11, 2011

There are a great number of these urls showing up daily. The forward (/) slash at the end of the url shouldn’t be there and it’s’ causing the 404 error.

Many of the tags appearing in these urls have been deleted from my blog ages ago and may be re-occurring as 404 errors again, after removing them with the Google webmaster tool.

I don’t know if there is some type of Disallow I need to enter in my robot.txt or not.

I’m allowing my tags to be indexed and not allowing my categories, archives, etc., to be indexed.

My Worpress permalink (Custom Structure) is set as /%postname% . I changed that structure early this year or later part of last year when I changed my theme to the current one.

I deleted the HeadSpace SEO plugin recently and started using the All in One SEO plugin.

Also, many old tags that I deleted ages ago are appearing in the 404 page error urls as well and they seem to be re-occurring over time after deleting them with the Google Webmaster Tool.

I appreciate any help that will lead to a permanent solution.