Strange-the page is loading twice

Today, flyer every y me that the page is loading twice, very strange.

And this is my step to solve the problem.

1. Open firebug and discoverTwo requestsOf home. Do page
(HTTP action-Get ).

2. Open httpwatch in IE and do the same test, onlyOne
RequestOf home. Do.-Oh, Firefox you must be kidding.

3. Use Web Developer toolbarDisable 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. AlsoTwo
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 test myself using binary search.

7. Finally, I f found the bug:Alt = "" src = ""/>

Conclusion, if the HTML page hasIMGTag with emptySRC
Property, then the page will be loaded twice in Firefox.