Alt text is used by search engines as part of indexing a web page. Image size attributes are used by browsers to render the web page more quickly. Some failures identified by Linkbot are browser dependent. But the latest browsers by Microsoft and Netscape will successfully interpret this malformed address. It is not always apparent what is the actual error being reported by Linkbot.
Web pages are complicated.
For instance, there might be a broken link with no anchor. Linkbot will identify this broken link. But the only way to find it is to look at the raw html text. And then you may decide it does not need to be fixed. Some sites have hundreds or even thousands of links listed as broken, but not really broken.