html - How to load bootstrap thumbnail images -

I have started using bootstrap for a project, and in particular, on the thumbnail component, the following sample code was shown Gone:

  & lt; Ul class = "thumbnails" & gt; & Lt; Li class = "span 4" & gt; & Lt; A href = "#" square = "thumbnail" & gt; & Lt; Img data- src = "holder.js / 300x200" alt = "" & gt; & Lt; / A & gt; & Lt; / Li & gt; ... & lt; / Ul & gt;  & lt; Img & gt; Report the use of   
 to replace the normal  src  attribute at  data-src > tag.  
 I think my thumbnail should work, I should use  data-src  instead of  src  for images, but not so It looks like I'm able to load images only by defining the  src  attribute.  
 Is this a typo in the documentation, or am I  data-src ?    
  Div class = "post-text" itemprop = "text"> 
 I believe that the bootstrap men are  data-src  Holders  are using  src , the only reason being is the  holder Due to Js  you should use  src  instead of  data-src , because because of the  data-src  is used only for the Javascript library The generic feature for specifying the location of the image is generated (source :)  
  Why are they using the  data-src  in the documentation?  I think the syntax also by the library  & lt; Img src = "holder.js / 100x200" & gt; & Lt; / Img & gt;  is accepted, when we reach the page, there is a 404 error even when it appears in the image, whenever the image is displayed, because there is no file in the specified path, it is strange.  
  In that documentation code?  I do not really know if this is a mistake. But I'm sure you should use  data-src  instead of  src  in the thumbnail.