If you've ever developed HTML emails, you're likely aware of the challenge they present. Unlike modern web browsers that largely adhere to web standards, email clients like Microsoft's Outlook have unique quirks that can make your perfectly crafted email look different from what you intended.
After upgrading to IE11, web page layout may be broken. The most common reason is the web page runs in a newer document mode in IE11. However, the layout issue might still occur even if the document mode is same as before. This is because IE11 uses natural metrics for font rendering while previous IE versions use Windows Graphics Device Interface (GDI) metrics.
External file references in web page like: JavaScript and CSS may block page rendering. They force the browser to wait for the files to be downloaded, parsed and execute. Assuming that there is a JavaScript file reference which needs 2 seconds to be loaded, then the browser will stop rendering until the JS file is loaded after 2 seconds. We need to eliminate any potential blocking external JavaScript and CSS files when optimize web page.