HTTP Codes advice...

I seem to be getting a lot of http error codes listed on my stats page. Does this effect me with my SEO in Google?

Also how do I get rid of them? Most of the 404 codes seem to be from google images finding images from my old site before it was completely re-done around 4 mths ago. These images are no longer on my server but google is still using them in search results?

My HTTP codes listed as of today are as follows:
404 Document Not Found 926 58.4 %
302 Moved temporarily (redirect) 621 39.2 %
400 Bad Request 19 1.2 %
403 Forbidden 10 0.6 %
301 Moved permanently (redirect) 5 0.3 %
206 Partial Content 2 0.1 %

Thanks in advance for those taking time to offer advice...

Yes, Google does try to find pages several times before it 'gives up' and deleted pages from the index for good. Best practise is to always use 301 redirects to new pages/images/etc. However, I guess it depends on the effort you have to put into 'cleaning it all up'. Maybe you can do something about the 302 redirects and change them to 301s (permanent redirect). I have not seen the error 400 on our websites yet, so maybe you can find out what's happening there, too.

In terms of rankings, I have no definite information and can only guess/hope that it does not negatively affect your rankings for existing pages that Google can't find everything that it tries to find.

I don't think Google would penalise you unless they decide that you are doing something blackhat. Having those stats is not anything unusual or alarming.

Depending on how popular your web site is you will always attract people that are looking for back doors through free or open source software.

For example here is a snapshot of some 404's one of my web sites has received:

/PMA/main.php
/myadmin/main.php
/phpMyAdmin-2.6.3/main.php
/mysqladmin/main.php
/phpMyAdmin-2.6.2-rc1/main.php
/mysql-admin/main.php
/admin/phpmyadmin/main.php
/phpmyadmin/main.php

All of these requests are people searching for an unprotected installation of the popular open source package called phpMyAdmin. I don't even have it installed on the server!

But these types of requests will generate 404, 400 and 403's.

In short you will never stop these entirely, you can reduce them by setting up custom 404 error pages etc via .htaccess but you will always get some of these appearing.

HTH