favicon about zen classic

在 http://drupalcamp.百加一講壇.tw/ 用了leowang的logo[in http://drupalcamp.百加一講壇.tw/ , i use leowang's logo]

我用zen classic theme, 並改了shortcut 如下箭頭[I use zen classic theme and changed shortcut as follows、look at the arrows]：

firefox將小圖顯示出來如下箭頭[firefox shows the favicon correctly as shown below, look at where the arrow points to]

IE7未將小圖顯示出來如下箭頭[IE7 can not show leowang's favicon as shown below, look at where the arrow points to. it shows the original drupal logo]

用iPhone 3GS, 沒有leowang's logo也沒有drupal logo. [In iPhone 3GS，nothing shown, not even the drupal logo.]

接著我又用iPhone 3GS試 drupaltaiwan.org，沒有drupal logo。[Then I try iPhone 3GS with drupaltaiwan.org, no drupal logo]
接著我又用iPhone 3GS試 drupal.org，首頁有drupal logo, 其他頁不一定有drupal logo。[Then I try iPhone 3GS with drupal.org, front page displays drupal logo, but not guarantee to see drupal logo on every page.]

我曾讀了一些favicon的資訊，用32x32的png file.見第一圖。[i have read favicon documentation, and used 32x32 .png file. as the first picture shown]

問題：是否一定得用.ico file。可介紹一個可將.png(or .jpg)檔轉成.ico的軟體給我嗎？
question: Do i have to use .ico files? and can someone provide a link to a software that can convert .png or .jpg to .ico files.

謝. thanks.

Note:favicon的重要性。(the importance of favicon)
可能大多數的人認為favicon不重要，但是，在mobile internet，若favicon設不對, iPhone(或其他手機)上bookmark時就顯示不出logo,會很難看，你的網站就遜了！
Most of us may think that favicon is not important. But in today's world, mobile internet gets real popular. iPhone will not show your site on its screen with your site's logo(which is the identity of your site). And your site will look very unprofessional.

以上看法若不正確請告知,謝謝。(Please let me know if the above view is inocrrect. thanks)。