So many web browsers like Firefox, Internet Explorer, Google Chrome, Opera are available for us. Each of these browsers uses different webkit engine to render website. Hence the website displayed in one browser may not look like that in other browser.
This may be little issue for users but for webmaster and web developers this is a big issue as they need to keep checking website in all popular browsers to make sure Cascading Style Sheets (CSS) of website is renders properly which is really time consuming and troublesome task.
Here is CSS Selector Shell new Google app to let you to test how a given browser parses CSS text by inserting a style element into the document and then reading the cssText back programmatically. CSS Selector Shell is based on powerful Dojo Toolkit which is extremely useful in diagnosing problems or understanding the differences between browsers when interacting with your Cascading Style Sheets.
Screenshot of CSS Selector Shell Google App