I have an issue with one of my websites. One of the pages of the format http://www.example.com/page.html is indexed several times by Google like this: http://www.example.com/page.html/page1/ and so on. Basically, for some reason Google is indexing this page ending in .html with a slash (/) at the end. As a result, all internal links on this page become altered (page.html/page1/page3/page5/ and so on) resulting in a high number of apparently different pages showing the content of the oringinal page.html, only not styled. All these pages are indexed by Google and I am worried that they may see it as dup content. I couldn't find any errors with the html code on page.html.
Does anyone have any idea what could be causing this issue? Or why, instead of showing a 404 error when added the slash at the end the page.html file loads fine?