What is Develop that suddenly appears in menu after 3.1 update?

Question

After an automatic upgrade through Software Update, Adobe Reader doesn't work right. According to Adobe, it is current. Something called Develop appeared in the menu and something called DeBug disappeared. I can find nothing to explain these happenings. No directions as to their use. Could someone please explain? There always seems to be errors in opening web pages although most of the time the pages do load. I use Disk Utility religiously. I suddenly had Safari tell me that a security check was going to be needed. Never happened before so I said okay but then a window said I had to download a program and the certificate was expired. I refused permission to allow. It quit. I have never had a problem with 10.+ until now. I spent three hours going through forum messages and could not find anything about Develop or DeBug. Help, please.

Answer 1

Develop replaced the Debug menu that was always there in Safari 3.0.4 but had to be activated from Terminal or via a third party application. Now it's easier.
From Safari's Help menu:
The Develop menu provides tools for web developers creating websites for Safari and Mac OS X.
NOTE: If the Develop menu does not appear in the menu bar, open Safari preferences, click the Advanced tab, and select “Show Develop menu in menu bar.”
The Develop menu options are:
Open Page With: Lets you open the displayed webpage using a different web browser on your computer. All web browsers on your computer are listed in the submenu.
User Agent: Lets you change how your web browser is identified by the web server. Use this option to “spoof” the web server into thinking that you’re using a web browser other than Safari, to investigate whether the server is providing different content to different web browsers.
Show Web Inspector: Opens the Web Inspector. The Web Inspector lists the categories of resources found on a webpage, such as documents, style sheets, and scripts. It lets you view and search the page’s source code, Cascading Style Sheet (CSS) information, DOM trees, visual DOM metrics, and DOM properties. The Web Inspector also contains the error console and network timeline.
Show Error Console: Opens the Web Inspector’s display of HTML and XML syntax errors and warnings. The error console also displays JavaScript errors output from console.log, console.error, and console.warn.
Show Network Timeline: Opens the Web Inspector’s timeline of when your page’s subresources were loaded. This is useful for investigating how to improve the speed at which your webpage loads.
Show Snippet Editor: Opens a window you can use to quickly test small fragments of HTML, without requiring you to open an entire webpage.
Disable Caches: Causes Safari to retrieve a subresource from the web server each time the subresource is accessed, rather than using a cached copy.
Disable Images: Causes Safari to show the alternate content where images would be. This is useful for making sure your webpage has appropriate alternate content.
Disable Styles: Causes Safari to ignore all Cascading Style Sheet (CSS) styles. This is useful for investigating some types of page layout problems on your website. If you have a style sheet set in Safari advanced preferences, it continues to be used.
Disable JavaScript: Causes Safari to ignore all JavaScript. This is useful for investigating certain problems with how parts of websites behave, and for testing how a website performs on web browsers that don’t support JavaScript or have JavaScript disabled. You can also turn JavaScript off and on in the Safari security preferences.
Disable Runaway JavaScript Timer: The Runaway JavaScript Timer is used to interrupt the execution of very slow JavaScripts, so you can regain control of Safari. Disabling it is useful for some types of automated testing.
Disable Site Specific Hacks: Some versions of Safari contain special-case code that allows certain webpages to behave normally while Apple engineers work with you to find a better long-term solution. This option turns off that special-case code, so you can test your long-term solutions.