One common mistake that many newcomers developers make is when deploying static content.
Magento 2 typical command to deploy static content is
$ php bin/magento setup:static-content:deploy
However, there is an important aspect to take into account. The above command uses the default options. This means that only the
en_US language is deployed. If you site is using other locales you must explicitly deploy the static content for them.
If, for example, you use
en_CA you must run
$ php bin/magento setup:static-content:deploy en_US en_CA
This will avoid the 404 errors when going into the frontend (or even the admin) of your magento store 🙂
Also, do not forget that is you are running magento in developer or default mode you will need to use the
-f option to force the deployment.
Hope this helps!