Notice: Undefined offset: 1 in _resp_img_replace()

I am getting this same error most pages as well..

Here is the page I am getting this on. as an attachment:

Looking at the line the error occurs, the only thing I can think of is that you either have an img tag without a src attribute, or an img tag where the value of the src attribute is encapsulated in single quotes in stead of double quotes. Can you check if that's the case?

I was having a similar issue after enabling a new module on my site to handle Twitter 'things' (http://drupal.org/project/twitter), each instance of an image was returning this error; I checked the img tag as per your comment and I did discover that the src attribute was doing a funky double quote dance.

src=""path""

So I modified some of the code, tested, and ran some debug checks; however it didn't stop the error message.

Eventually I decided to disable, uninstall, and reinstall resp_img to see if there was some unseen hang-up; nope, but while toggling settings and running tests I noticed that disabling resp_img for blocks (resp_img_block_enabled) caused the error to cease.

I'm still looking into why this is the case, but with less fervor as it is no longer reporting the error; I am not totally convinced it is resp_img's fault since it was running fine before the latest module addition.
Hope this helps anyone out there with this error.

Attached is a patch that removes the error by not attempting to change images when the src is not found by preg_match('/src=("[^"]*")/i', $img, $src);

Old issue, I think you better update to the picture module

Well I definitely have the latest version and I also get this error.
I changed the offending line to $src = sizeof($src)>0 ? $src[1] : ""; but I am sure there is a better way to fix this.