'Veranda' is specified for the font. Somehow, Safari assigns a larger value to the text input box than other browsers (FF and IE) and ends up pushing the search button below the input text box rather than to its right.
It happens on both Windows and Mac OS X. On Windows, I tested with the latest version of Safari. On Mac OS X, I used Safari with a trunk build of WebKit.
Baidu is #1 search engine in China.
Firefox also puts the button below the text field.
Created attachment 15888 [details]
text input box with a few different fonts
Compare the width of text boxes with different fonts in Safari, IE, FF and Opera on Windows.
On Mac OS X, FF has the same problem, but on Windows FF does not. Neither does Opera. The root cause of this bug may be the same as that of bug 14907.
In Safari, I can type '12345690' 3 times and additional '123456' (i.e. exactly 36 digits) in attachment 15888 [details]. The size of text input field is 36, but in other browsers, I can enter only up to 29 or 30. I wonder what other browsers use to determine the width. It's not certain EM because it would make the width larger (rather than smaller) if it were EM they use. Anyway, a lot of web sites (in East Asia) seem to depend on the behavior of other browsers....
*** Bug 15261 has been marked as a duplicate of this bug. ***
It has been hypothesized that other rendering engines use some sort of "multiplier" to account for the fact that fonts aren't monospace. We use the "size" value as an em value for width, thus make the input wider.