See your code in action here. It works great in Firefox, Chrome, and IE, as I just tested.
<html xmlns="http://www.w3.org/1999/xhtml"> <head> </head> <body> <a href="https://twitter.com/share" class="twitter-share-button" data-url="http://www.3eesho.com/magazine/index.html" data-text="issue2 now" data-via="3eesho" data-hashtags="ipad,health,arabicmagazine">Tweet</a> <script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");</script> </body> </html>
Take a look at the screenshot below: the performance of your code in IE 8, Firefox 9, Chrome 16. works as expected.

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