Is liquid layout (everything in % and font-size in 'em') good or creating multiple css file for different resolutions or browsers with help of Javascript good?
I am a aspiring web designer, and want create a universal accessible web pages?
The trend is moving towards 'responsive web design' rather than liquid layouts measured in percentages.
CSS3 introduced media queries, which allow you to serve different styles depending on device resolution, without needing to resort to Javascript, so this makes it far more flexible when designing for multiple devices.
Ethan Marcotte is the person who popularised the term responsive web design - in fact, he basically wrote the book on it. His article on A List Apart is a good place to get started:
For some inspiration on what can be achieved with media queries and responsive web design, check out http://mediaqueri.es/