Original address: http://www.ncloud.hk/%E6%8A%80%E6%9C%AF%E5%88%86%E4%BA%AB/umbraco3css-javascript/
CSS & Javascript
Looking at our homepage It was obvious that the CSS and JavaScript templates were not added. Include navigation in the root directory of this site (for example: "C:\inetpub\wwwroot" which may be different depending on your installation type), copy the Css\style.css file in Windows Explorer to [your site's root directory]\ CSS folder (regardless of whether your Umbraco instance has replaced Umbraco-for example: "C:\inetpub\wwwroot". Now refresh your page in the browser and you'll see the page with the style.
Note-You can manually create your CSS file using the Umbraco UI. Settings > StyleSheets > ... > + create creates a style sheet named style (no need to add a file suffix. css), and then pastes the CSS code I need. Both of these methods should be careful not to include your HTML auto tag-the output generated by Umbraco, which means you only need something you want to write and what you need.
Next, copy the Modernizr-2.0.6.min.js file from the initialization package to the Scripts folder in the site-we'll update the new template to see/scripts instead of/js. To do this requires us to change the path of the script file in Settings > Templates > Homepage , and finally click Save.
<script src= "Scripts/libs/modernizr-2.0.6.min.js" ></script>
Note- You can also manually create your JS file Settings > Scripts > ... > + Create (Again, you do not need to add the file suffix name. js, but you need to select. js in the Type drop-down option). The reference template here is "scripts/myfile.js".
Now we only use Chrome developer tools or Firebug while browsing http://localhost you will find that the Network tab does not report any lost assets/files-if it is there is a look and fix any errors/check files should be in the right place.
"Original: Https://our.umbraco.org/documentation/using-umbraco/creating-basic-site/CSS-And-Javascript"
Umbraco (3)-CSS & Javascript (translating documents)