When special characters are used, some browsers will either ignore the layer or render it incorrectly. This may result in JavaScript errors, because the layers will not be recognized as part of the Layers array. The underscore character can safely be used to concatenate strings to form a single word for the name property. Do not begin the name property with a numeric value.
Numbers are different from character strings in values.
Names that begin with a numeric value, or names using only numeric characters, will cause JavaScript syntax errors. Use only a single word for a layer name. Multiple words with spaces will cause JavaScript syntax errors. Assign a unique name to each layer. JavaScript errors can occur if a layer and an image have the same name.