Strange - the page is loading twice

Today, Flyer notify me that the page is loading twice, very strange.

And this is my step to solve the problem.

1. Open firebug and discover two requests of home.do page (HTTP action - GET).

2. Open HTTPWatch in IE and do the same test, only one request of home.do. - oh, firefox you must be kidding.

3. Use Web Developer Toolbar to disable all JavaScript execution, and firebug also find two requests of home.do page.

 4. I doubt whether firebug is ill,  i disable firebug and enable another tool to inspect the HTTP traffic - HTTPWatch for firefox. Also two requests.

5. I open the source code of the page, and to see whether there is some special meta-data in the head, nothing is found.

6. Copy the entire source code of the HTML page to local Apache server, and test myself using binary search.

 7. Finally, i f found the BUG: <img class=”my_display_image” alt=”" src=”" />

Conclusion, if the html page has img tag with empty src property, then the page will be loaded twice in firefox.