I want to customize a bit the look of the ISIS admin template in Joomla 3. Need to add a few custom css for colours, and hide a few elements here and there. What is the best way to do this?
Custom.css for Joomla 3.4.1 and later
This method is the easier for custom CSS overrides for the admin template. Simply create a
custom.css file and place it inside the css folder of the ISIS template, like so:
The template will load this css file last, so any css rules declared there, will override the core ones.
Remember that this is a new feature introduced in Joomla 3.4.1. Earlier versions had no core - support for this.
Older Joomla Versions: Clone the template
Before introducing the
custom.css feature for Joomla admin template, you had to copy/clone the ISIS template, inside the template manager, and then work it like a totally separate custom admin template. This method will allow a lot of flexibility in creating a customized template, not only on the css level.
However, with the rather quick speed that Joomla core is changing, your template might need some extra work after any Joomla updates, to support any possible new features.
In any case, at this point all Joomla 3 installations should be up to date with the latest versions (current version 3.5.1). Versions before 3.4.8 are vulnerable - consider to update A.S.A.P.
If you do not want to redo all stuff whenever you update Joomla, create a copy of the template and use template manager to modify its files. If you wish to modify files using local editor, make sure your file editing software can save files with utf-8 encoding.
Please see below documentation: https://docs.joomla.org/J3.2:How_to_use_the_Template_Manager
It's even easier than the other answers suggest. In ISIS you can upload a new css file custom.css. You need to upload this in:
The template will automatically pick it up and start using it. It also loads it last so your styles will be more specific. This feature is available from Joomla! 3.5 onwards.
The reason this would be preferable to duplicating a template is because:
a) In the event of template updates you would need to maintain your duplicate template.
b) That leaves you open to security vulnerabilities.
c) You are probably only making small changes, so you don't need to copy an entire tempalte.