b.k.

jquery

$("*") Selects all elements Try it 
$(this) Selects the current HTML element Try it 
$("p.intro") Selects all <p> elements with class="intro" Try it 
$("p:first") Selects the first <p> element Try it 
$("ul li:first") Selects the first <li> element of the first <ul> Try it 
$("ul li:first-child") Selects the first <li> element of every <ul> Try it 
$("[href]") Selects all elements with an href attribute Try it 
$("a[target='_blank']") Selects all <a> elements with a target attribute value equal to "_blank" Try it 
$("a[target!='_blank']") Selects all <a> elements with a target attribute value NOT equal to "_blank" Try it 
$(":button") Selects all <button> elements and <input> elements of type="button" Try it 
$("tr:even") Selects all even <tr> elements Try it 
$("tr:odd") Selects all odd <tr> elements Try it