CSS and master page - Sharepoint online - Office 365

Question

I created a custom .css file and dumped it in /Style Library/custom/corev15.css I just created the 'custom' folder and created a duplicate of the original (/_layouts/15/1033/styles/Themable/corev15.css).

After doing that I enabled the "SharePoint Server Publishing Infrastructure" feature under the main site collection features. Then, under "Master Page" I specified the alternate CCS URL using the custom .css that I created. I checked the option "Reset all subsites to inherit this alternate CSS URL" so that all the remaining 38 sub sites within my site collection use the same .css file.

The only changes I made in the custom .css file was to the top navigation menus (no word wrap on the drop-downs, font size, etc.). Am I missing something? The reason I'm asking is because the changes took affect after I checked-in the .css file in SharePoint designer; however, when sub-sites try to add a certain background image or color scheme, the changes that they apply don't show up. There are some that show up partially (see images below):

Am I supposed to reference this custom CSS any where in the Master file - seattle.html ? If so, where?

Answer 1

SharePoint 2013 by default applies corev15.css to all pages, so you don't need to make a copy and append your styles.

Instead put only your custom CSS into your own corev15.css file and set the link (as you already did).

SharePoint 2013 will then load the default corev15.css and afterwards load your custom one and apply the changes you made.

UPDATE

Just to clarify, you still need a reference to your custom CSS like this:

<!--PS: Start of READ-ONLY PREVIEW (do not modify) --><link href="generalglassintl.sharepoint.com/Style Library/custom/corev15.css" rel="stylesheet" type="text/css"/> and also -> <!--SPM:<SharePoint:CssRegistration Name="/Style Library/custom/corev15.css" runat="server"/>-->

But inside your "/Style Library/custom/corev15.css" you'd only need to put the CSS you want to apply to change the look & feel of the top navigation bar.

Answer 2

The above answer is not right. It is totally unnecessary to touch corev15.css.

These are the steps to apply custom CSS to SharePoint site hosted at Office 365.

1. Find "Site Collection Features" setting and enable all features with name "publishing" in it.
2. Find "Manage Site Features" setting and enable all feature with name "publishing" in it.
3. Find "Master Page" setting link under "Look and Feel".
4. Click "Alternate CSS URL". This is where you apply your own CSS file.
5. Upload a CSS file to any document library. Ideally to "Style Library".
6. Go to step 4 and choose your uploaded CSS file.