Inline styles and scripts

When you want to make a quick change to a web page, it's often tempting to slip an inline style, script or event handler into the markup. This is a bad idea, because it adds more weight to the page, loses the benefit of caching, potentially blocks parallel downloading and can slow down the rendering of the page. On top of that it makes maintenance and code re-use that much more difficult.
Performance effects of inline scripts and styles

Testing

The Firebug extension "Inline Code Finder" will show where inline scripts and styles have been declared.

Solution

Make Javascript and CSS external.