In the top of the webpage be sure to put the DOCTYPE. This tells the browser that it has to render the layout according to the to the terms of the W3C (World Wide Web Consortium), the organization that creates the standards for web browsers.

The first three letters DTD state the “document type definition”. This tells the browser to render the page according to the specifications of the W3C. the HTML 4.01 is the current W3C standard version. Browsers can render to that standard and below.

“Transitional” permits pages to render properly even if the code coming is not the latest standard. Some browser display “strict DTD” meaning that your markup must comply strictly with the XHTML standard.

Even though you’ll be using “Transitional DTD” this does not mean you can be lazy with your coding. You must adhere to strict compliance in all of your work or pay for it with endless headaches in the future.

Speaking of strict compliance, it’s always handy to remember to add the Content-type Meta Tag into your header. This line of code simply tells the browser that you are using Western European language structures (Latin based.) while your page will most likely load fine without this code, it’s a good idea to keep it to ensure proper validation with the W3C standards. If it’s not there and you to go validate the CSS code, it will be rejected by the W3C. It sounds more complicated than it is. Just put the code in, or make sure that your web design software does it for you.

source: http://www.htmlcodetutorial.com/css/_SETUP.html

            Diigo