So far, we have created a theme that looks nice on most modern browsers, such as Google Chrome, Firefox, Opera, and Safari, but there is a chance that we want to support Internet Explorer. At this moment, if we open our application using IE, the theme may not work well. This is because IE doesn't support many of the new goodies of CSS3.
So, we need the Sencha CMD tool when compiling or building the theme makes sliced images for our custom theme. In this way, older IE versions or browsers that not support CSS3's new goodies will then be able to look almost the same, thanks to the use of images. To do this, let's open the
my-custom-theme/sass/example/custom.js file. Now you will see this line commented: