Matthew Inman on seomoz has written an article “15 CSS Properties You Probably Never Use, but perhaps should”. These are all CSS level 2 properties but some of them don’t work in all browsers, so make sure and test things out before putting them into use.
clip: rect(5px, 40px, 45px, 5px)
From iBloom Studios
A good way to visualize the clip attribute is if you take a piece of paper with a rectangle cut out of it and place it on top of a photo (just like using a Photoshop layer mask). The area of the rectangular hole, allowing the layer behind it to show through, is what the clip property will specify.
visibility: (inherit | visible | hidden)
For practical purposes, the difference between these two properties [visibility and display] is that when you hide information using the visibility property, the browser creates the appropriate amount of space in the browser window for the information when the page loads. When you use the display property, space for the information is not created until the element becomes visible.