I’d mentioned this bug when I use Safari 4 for the first time before. It is something to do with the lightbox javascript effect that cover the whole page and remain stuck there, when I tried to add URL.

It appear that, this is not Safari 4 bug, but related to the webkit that Safari 4 use. If you encounter this bug , please install the webkit by following these steps.

1. Download webkit (the version as of today: WebKit r41707) from webkit website.

2. Run ‘run-nightly-webkit‘ file until it stopped (with message ‘XXX files copied‘)

Thanks to Jonas, who point this out.