When dealing with Event handler Attributes you will often have to nest quotes, especially when you pass a string value into a JavaScript function inside the Event handler Attribute. The way this works is that both XHTML and JavaScript will accept single and double quotes as indicating strings, so long as the one that starts the string is the one that ends it; i.e. if you open with a double, you had better close with a double, likewise with single quotes. Also, if you're inside a string that was started with double quote, it won't treat single quotes as string terminators (that would end the string) and vice versa. If you always use single quotes in JavaScript and double quotes for XHTML then you won't be led astray unless you have more than one layer of nesting (possible, but we don't need it in this class).