Customizations to the Office 365 top navigation bar in SharePoint Online revert to the original settings
Consider the following scenario.
You make customizations to the Office 365 top navigation bar in SharePoint Online by changing any .css class that begins with the following:
You discover that these changes have reverted to the default settings.
To work around this issue, use SharePoint themes or Office 365 themes.
For more information about themes in SharePoint Online, go to SharePoint Site Theme.
For more information about Office 365 themes, go to Personalize your Office 365 experience by selecting themes.
This issue occurs because overriding .css classes that begin with ".0365cs-" isn't supported. These classes are frequently updated across the Office 365 service as new functionality is deployed. When this kind of updating occurs, changes may be overwritten.
Still need help? Go to SharePoint Community.