the name of the CSS class or the object with styles that will be applied to the view container
<style>
.myClass {
    font-style: italic;
}
</style>
webix.ui({
    css:"myClass",
    view:"dataview",    // any component
    ...
});
Setting the parameter, for example, to the "myClass" value will produce HTML like this:
<div class='myClass'>...</div>
css can also be an object with styles:
webix.ui({
    view:"dataview",    // any component
    css:{"font-style": "italic"},
    ...
});
This will produce HTML with a CSS class with an auto-generated name.
Note that for some components you will need to add !important to CSS rules to override the default ones.
webix.ui({
    view:"toolbar", // or other components
    css:{"background":"#ccc !important"}
    ...
});