top Attribute | top参数属性

Sets or retrieves the position of the object relative to the top of the next positioned object in the document hierarchy.

dhtml语法

HTML	{ top : sTop }
Scripting	object.style.top [ = sTop ]

DHTML可能的值

sTop

Variant that specifies or receives one of the following values: auto Default. Default position according to the regular HTML layout of the page. length Floating-point number, followed by an absolute units designator (cm, mm, in, pt, pc, or px) or a relative units designator (em or ex). For more information about the supported length units, see css length units reference. percentage Integer, followed by a percent sign (%). This value is a percentage of the height of the parent object.

The property is read/write for all objects except the following, for which it is read-only: currentStyle. The property has a default value of auto. The Cascading Style Sheets (CSS) attribute is not inherited.

Expressions can be used in place of the preceding value(s), as of Microsoft® Internet Explorer 5. For more information, see about dynamic properties.

remarks

the top attribute should be used only when the position attribute is set; otherwise, the value of the top attribute is ignored.

because the value of the top property is a string, you cannot use the property in script to calculate the position of the object in the document; instead, use the pixeltop or the postop property.

for more information about how to access the dimension and location of objects on the page through the dynamic html（动态html，即dhtml）燿ocument object model (dom), see measuring element dimension and location.

Examples

The following examples use the top attribute and the top property to change the position of the object.

This example uses an inline style to set the position of a div object.

<div style="position:absolute;top:100px">
. . . </DIV>

This feature requires Microsoft® Internet Explorer 4.0 or later. Click the following icon to install the latest version. Then reload this page to view the sample.

This example uses inline script to change the position of the image set by an inline style. The change occurs during onmouseover and onmouseout events.

<img src="cone.jpg" style="position:absolute;
top:80px;" onmouseover="this.style.top='100px''"
onmouseout="this.style.top='80px'" >

This feature requires Microsoft® Internet Explorer 4.0 or later. Click the following icon to install the latest version. Then reload this page to view the sample.

是否符合公共标准

This property is defined in Cascading Style Sheets (CSS), Level 2 (CSS2) .

Applies To

A, ADDRESS, APPLET, B, BIG, BLOCKQUOTE, BUTTON, CENTER, CITE, CODE, currentStyle, CUSTOM, DD, defaults, DFN, DIR, DIV, DL, DT, EM, EMBED, FIELDSET, FONT, FORM, hn, HR, I, IFRAME, IMG, INPUT type=button, INPUT type=checkbox, INPUT type=file, INPUT type=image, INPUT type=password, INPUT type=radio, INPUT type=reset, INPUT type=submit, INPUT type=text, ISINDEX, KBD, LABEL, LEGEND, LI, LISTING, MARQUEE, MENU, OBJECT, OL, P, PRE, runtimeStyle, S, SAMP, SELECT, SMALL, SPAN, STRIKE, STRONG, style, SUB, SUP, TABLE, TEXTAREA, TT, U, UL, VAR, XMP

更多语法参考

pixeltop, posTop