YSlow: Avoid empty src or href More Recommendations

Rule Summary

Content
High
Easy
98%

Overview

Empty src or href attributes can cause multiple problems.

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Details from Yahoo!

You might expect a browser to do nothing when it encounters an empty image src. However, this is not the case in most browsers. IE makes a request to the directory in which the page is located; Safari, Chrome, Firefox 3 and earlier each make a request to the actual page itself. This behavior could possibly corrupt user data, waste server computing cycles generating a page that will never be viewed, and in the worst case, cripple your servers by sending a large amount of unexpected traffic.

recommends:

Empty image tags occur more often than you might expect. They can appear in two form:

  1. Straight HTML
    <img src="">
  2. JavaScript
    var img = new Image();
img.src = "";

Both forms cause the same effect: the browser makes another request to your server.

  • Internet Explorer makes a request to the directory in which the page is located.
  • Safari and Chrome make a request to the actual page itself.
  • Firefox 3 and earlier versions behave the same as Safari and Chrome, but version 3.5 addressed this issue (bug 444931) and no longer sends a request.
  • Opera does not do anything when an empty image src is encountered.

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