h1 {
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   text-indent:-9999px;
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   margin:0 auto;
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   width:400px;
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   height:100px;
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   background:transparent url("images/logo.jpg") no-repeat scroll;
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}

http://www.djavupixel.com/development/css-development/master-css3-ultimate-css-code-snippets/

Hiding text can be extremely useful to hide company logo. As logos are usually an image, you will want to use text indent to place it in a h1 tag for SEO (Search Engine Optimization). The technique we use is to hide the text far away off the screen, and apply a background image instead.

hide text indent trick thingy for css

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