For HTML 4, the answer is technically:
ID and NAME tokens must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens ("-"), underscores ("_"), colons (":"), and periods (".").
HTML 5 is even more permissive, saying only that an id must contain at least one character and may not contain any space characters.
The id attribute is case sensitive in XHTML.
As a purely practical matter, you may want to avoid certain characters. Periods, colons and '#' have special meaning in CSS selectors, so you will have to escape those characters using a backslash in CSS or a double backslash in a selector string passed to jQuery. Think about how often you will have to escape a character in your stylesheets or code before you go crazy with periods and colons in ids.
For example, the HTML declaration <div id="first.name"></div> is valid. You can select that element in CSS as #first\.name and in jQuery like so: $('#first\\.name'). But if you forget the backslash, $('#first.name'), you will have a perfectly valid selector looking for an element with id first and also having class name. This is a bug that is easy to overlook. You might be happier in the long run choosing the id first-name (a hyphen rather than a period), instead.
You can simplify your development tasks by strictly sticking to a naming convention. For example, if you limit yourself entirely to lower-case characters and always separate words with either hyphens or underscores (but not both, pick one and never use the other), then you have an easy-to-remember pattern. You will never wonder "was it firstName or FirstName?" because you will always know that you should type first_name. Prefer camel case? Then limit yourself to that, no hyphens or underscores, and always, consistently use either upper-case or lower-case for the first character, don't mix them.
A now very obscure problem was that at least one browser, Netscape 6, incorrectly treated id attribute values as case-sensitive. That meant that if you had typed id="firstName" in your HTML (lower-case 'f') and #FirstName { color: red } in your CSS (upper-case 'F'), that buggy browser would have failed to set the element's color to red. At the time of this edit, April 2015, I hope you aren't being asked to support Netscape 6. Consider this a historical footnote.
Best Answer
Well this is embarrassing... I found the solution I was looking for and it couldn't be simpler. I used the following code to get the desired result.
Valid Accept Types:
For CSV files (.csv), use:
For Excel Files 97-2003 (.xls), use:
For Excel Files 2007+ (.xlsx), use:
For Text Files (.txt) use:
For Image Files (.png/.jpg/etc), use:
For HTML Files (.htm,.html), use:
For Video Files (.avi, .mpg, .mpeg, .mp4), use:
For Audio Files (.mp3, .wav, etc), use:
For PDF Files, use:
DEMO:
http://jsfiddle.net/dirtyd77/LzLcZ/144/
NOTE:
If you are trying to display Excel CSV files (
.csv), do NOT use:text/csvapplication/csvtext/comma-separated-values(works in Opera only).If you are trying to display a particular file type (for example, a
WAVorPDF), then this will almost always work...