Table中table-layout:fixed样式的作用。

请看下面的html

< html >
     < body >
         < TABLE  cellSpacing ="0"  cellPadding ="0"  width ="100%"  border ="1"   >
             < TBODY >
                 < TR  height ="30" >
                     < TD  style ="WIDTH: 12px" ></ TD >
                     < TD  class ="BigCaption"  style ="WIDTH: 150px" > Web Domain : &nbsp; < SPAN  class ="WarningDescription" > * </ SPAN >
                     </ TD >
                     < TD >
                         < SELECT  id ="DWT189WebDomain" />
                     </ TD >
                 </ TR >
                 < TR >
                     < TD ></ TD >
                     < TD  vAlign ="top"  colSpan ="2" >
                        asfdassdgsdgfsdgfsdgfsdfffffffffffffffffffffffffffffffffffffffffffffsdgfsdfgsdgsdgfsdgfsdgsdg
                     </ TD >
                 </ TR >
             </ TBODY >
         </ TABLE >
     </ body >
</ html >

显示这个页面，含有Web Domain的TD的实际长度绝对大于150px的。因为受第二行的colSpan的属性影响了

< html >
     < body >
         < TABLE  cellSpacing ="0"  cellPadding ="0"  width ="100%"  border ="1"  style ="table-layout:fixed"   >
             < TBODY >
                 < TR  height ="30" >
                     < TD  style ="WIDTH: 12px" ></ TD >
                     < TD  class ="BigCaption"  style ="WIDTH: 150px" > Web Domain : &nbsp; < SPAN  class ="WarningDescription" > * </ SPAN >
                     </ TD >
                     < TD >
                         < SELECT  id ="DWT189WebDomain" />
                     </ TD >
                 </ TR >
                 < TR >
                     < TD ></ TD >
                     < TD  vAlign ="top"  colSpan ="2" >
                        asfdassdgsdgfsdgfsdgfsdfffffffffffffffffffffffffffffffffffffffffffffsdgfsdfgsdgsdgfsdgfsdgs
                     </ TD >
                 </ TR >
             </ TBODY >
         </ TABLE >
     </ body >
</ html >

这才是我要的效果！呵呵！