One of the new features for Safari 5 is the Develop mode. It allows web developers to debug HTML code on Safari. Before you can use this feature, you must enable the Develop menu first. Here’s how you can do it:
Click on Safari menu and select Preferences. In the preferences window, select the Advanced tab and then click the checkbox for Show Develop menu in menu bar.
The Develop menu will then appear in Safari menu bar. Select Show Web Inspector to inspect your HTML code. You can also activate extensions support by selecting Enable Extensions in Develop menu. Extensions let you add those missing features.