With new HTML5 Self Service portal, one of the key aspect is level of customization which it supports. One of the basic thing which everyone wants is to change look and feel of portal based on their requirement. Customization can be done very easily by adding the Custom.css file in the \Content\css website folder. Styles defined in the custom.css file overrides the default styles (defined in \Content\css\main.css) of the Self Service Portal.
Donato Pasqualicchio from Service Manager Community has published his blogs which provide details on how you can customize UI to your liking. You can refer to following links from his blog-
Please note that Microsoft is only supporting customization which are defined in these files – web.config, custom.css & sidebar.cshtml. During patching and upgrade to Service Manager 2016 we will ensure that these files do not get updated. The remaining files like (.cshtml/.css/.js/.dll) can be updated in patch or upgrade, which could result in loss of any customization. In case if you have any changes in .cshtml, .css , .js or .dll , then back them up before patch/upgrade and merge with them later.