Javascript – Paginating HTML document for printing with WebKit-based browsers

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.

In your CSS you can set the @page property as shown below.

@media print{@page {size: landscape}}

The @page is part of CSS 2.1 specification however this size is not as highlighted by the answer to the question Is @Page { size:landscape} obsolete?:

CSS 2.1 no longer specifies the size attribute. The current working draft for CSS3 Paged Media module does specify it (but this is not standard or accepted).

As stated the size option comes from the CSS 3 Draft Specification. In theory it can be set to both a page size and orientation although in my sample the size is omitted.

The support is very mixed with a bug report begin filed in firefox, most browsers do not support it.

It may seem to work in IE7 but this is because IE7 will remember the users last selection of landscape or portrait in print preview (only the browser is re-started).

This article does have some suggested work arounds using JavaScript or ActiveX that send keys to the users browser although it they are not ideal and rely on changing the browsers security settings.

Alternately you could rotate the content rather than the page orientation. This can be done by creating a style and applying it to the body that includes these two lines but this also has draw backs creating many alignment and layout issues.

<style type="text/css" media="print">
    .page
    {
     -webkit-transform: rotate(-90deg); 
     -moz-transform:rotate(-90deg);
     filter:progid:DXImageTransform.Microsoft.BasicImage(rotation=3);
    }
</style>

The final alternative I have found is to create a landscape version in a PDF. You can point to so when the user selects print it prints the PDF. However I could not get this to auto print work in IE7.

<link media="print" rel="Alternate" href="print.pdf">

In conclusion in some browsers it is relativity easy using the @page size option however in many browsers there is no sure way and it would depend on your content and environment. This maybe why Google Documents creates a PDF when print is selected and then allows the user to open and print that.