Which technology should one use while designing a web app - HTML5 + CSS3 or HTML4 + CSS2?

If I want to work on a web app with 2-3 months of timeframe in mind, which technology 开发者_C百科should I use? HTML5 + CSS3 or HTML4 + CSS2?

Few points I am considering

• Compatibility of browsers
• Ease of use (especially with IE)
• Advantages over html4
• Learning curve

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In most cases, I'd avoid any of the new elements introduced in HTML 5. They tend to need JavaScript in order to render correctly in some commonly used browsers, and don't provide much in the way of practical benefits today.

Some of the APIs can be useful, but need to be taken on a case by case basis … and still function in HTML 4.01 documents.

Avoid CSS 2 in favour of CSS 2.1 (since it better reflects what browsers actually do). Examine CSS 3 properties and selectors on a case by case basis, comparing benefits, browser support, and what happens in the cases that browsers don't support them.

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Neither. Don't get hung up about standards. Pick what ever features you need from what works in browsers. Design with Progressive Enhancement and Graceful Degradation in mind.