Javascript converts value types on the fly as needed. It's called "type coercion". If you're not aware of this, you may inadvertently introduce bugs to your code. more
The focus event of an input field in IE7 bubbles up to the window. You would never realize this unless your design involved opening a new browser window while updating the parent window's DOM with content that contains an input field that auto focuses. It's a specific use case, I know, but one I recently encountered at work. more
Usually, you want to render all markup server-side. There are plenty of reasons why, but the one you hear often is for better search engine optimization. It's because search engine crawlers don't evaluate JavaScript. Though, there are cases when rendering markup client-side is the right thing to do. more