WordPress: responsive images for mobile devices with the wp_is_mobile() function
The main problem with mobile devices is related to the bandwidth they can use.
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Web programming languages and standards.
Do I really need a CSS framework? Only if...
The answer to this question is not just a matter of taste or project requirements but it’s a simple test for your technical skills and basic knowledge of the theory behind CSS.
Using jQuery in WordPress: techniques for theme authors
jQuery techniques for working with WordPress themes.