It is never wrong to quote attribute values, and many people recommend quoting all attribute values even when the quotation marks are technically optional. XHTML 1.0 requires all attribute values to be quoted. Like previous HTML specifications, HTML 4 allows attribute values to remain unquoted in many circumstances (e.g., when the value contains only letters and digits). 
Be careful when your attribute value includes double quotes, for instance when you want ALT text like "the "King of Comedy" takes a bow" for an image. Humans can parse that to know where the quoted material ends, but browsers can't. You have to code the attribute value specially so that the first interior quote doesn't terminate the value prematurely. There are two main techniques:

* Escape any quotes inside the value with " so you don't terminate the value prematurely: ALT="the "King of Comedy" takes a bow".
* Use single quotes to enclose the attribute value: ALT='the "King of Comedy" takes a bow'.

Both these methods are correct according to the specification and are supported by current browsers, but both were poorly supported in some earlier browsers. The only truly safe advice is to rewrite the text so that the attribute value need not contain quotes, or to change the interior double quotes to single quotes, like this: ALT="the 'King of Comedy' takes a bow".
Posting Copy and Paste HTML 
For those wanting to post direct Copy and Paste HTML on screen without the use of spaces or *s etc. and the need to explain those substitutions: Use &lt; to substitute for each opening tag < in each tagged set of HTML. Example, typing the following: &lt;a href="">&lt;img src="">&lt;/a> Will show up on screen as: <a href=""><img src=""></a>
HTML for Lists 
1. Bulleted Lists: <ul> begins a bulleted, indented list. Each item in the list is then prefaced with the <li> tag. It is not necessary to insert a break at the end of each line -- the <li> tag automatically creates a new line. 

* with <li type=disc>
* with <li type=square>
* with <li type=circle> 

2. Numbered Lists: <ol> begins a numbered, indented list. Each item in the list is then prefaced with the <li> tag. You need to close the list with the </ol> tag. Note: You can expand the <ol> to specify the TYPE of numbering:

<ol> 1 (decimal numbers: 1, 2, 3, 4, 5, ...)
<ol type="a"> a (lowercase alphabetic: a, b, c, d, e, ...)
<ol type="A"> A (uppercase alphabetic: A, B, C, D, E, ...)
<ol type="i"> i (lowercase Roman numerals: i, ii, iii, iv, v, ...)
<ol type="I"> I (uppercase Roman numerals: I, II, III, IV, V, ...)