1) Cascading Style Sheets (CSS) isn’t case sensitive. Nonetheless, text style families, URLs to pictures, and other direct references with style sheet might be.
2) All Selectors language structure is case-insensitive inside the ASCII extend (for example [a-z] and [A-Z] are equal), aside from parts that are not under the control of Selectors.
3) The case sensitivity of document language element names, attribute names, and attribute values in selectors rely upon the document language.
4) The trick is that on the off chance that you compose a record utilizing an XML declaration and an XHTML doctype, at that point the CSS class names will be case sensitive for certain browsers.
5) It is a smart thought to abstain from naming classes where the main contrast is the situation, for instance, div.myclass { …} div.myClass { … } If the DOCTYPE or XML declaration is ever expelled from your pages, even accidentally, the last example of the style will be utilized, paying little respect to the case.