CONSIDER A BROWSER AS YOUR MOST IMPORTANT DEVELOPER TOOL
For web developing, it is indispensable to run several desktop and mobile browsers, for better controlling and comparing of the HTML pages and for platform and browser checking.
Chrome or Firefox (both running on Windows, OSX, Android, Firefox also on iOS)
Both browsers can be enhanced with add-ons (Firefox) or extensions (Chrome) like “Color Picker”, “WhatFont”, “Copy Plain Text” and similar. Search the respective pages for Firefox and Chrome. Chrome has already a built-in web developer tool called “element checker” which is extremely useful (CMD-ALT-I or right-click on a page’s element that should be inspected).
The Developer menu should be enabled. Click on the 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. This will give lots of web-developing related options, like code inspector and more.
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.
If you have the impression that Safari is not showing the latest updates of your HTML doc, then again, empty the cache of Safari (ALT-CMD-E) and then reload the page.
Explorer (Windows), Edge (newest Windows 10)
Since Explorer still has a significant market share, websites must also be checked with it. Edge is WC3 compliant, and Explorer 11 is satisfyingly W3C compliant. Older versions, especiall below version 10, have infamous limitations which forced web designers to implement conditional comments into their code, like
<!--[if IE 7 ]> <p>Only IE 7 will see this</p> <![endif]-->
If you are not running a larger corporate website, you can actually pass these conditional comments, as the vast majority of Windows users have Explorer 10 at least.