下面两种方法自适应宽和高，zhenzhai推荐使用CSS方法；
一、CSS方法；
主要是在CSS设置最小值和最大值(max- 100px; max-height: 100px; expression(this.width >100 && this.height < this.width ? 100: true); height: expression(this.height > 100 ? 100: true);)
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><style type="text/css">
a img{border:0;}
a img
.imgthumblist { margin: 0 3px; padding: 0; list-style: none; } /*\*/ * html .imgthumblist { height: 1%; }/**/ *>.imgthumblist { overflow: hidden; } .imgthumblist li { float: left; display: inline; text-align: center; background: #F0F9FF; 108px; height: 163px; w\idth: 100px; he\ight: 155px; overflow: hidden; border: 1px solid #B9D0ED; padding: 3px; margin: 3px; } .imgthumblist li.list1line { height: 123px; he\ight: 115px; } .imgthumblist li.list2line { height: 143px; he\ight: 135px; } .contentL .imgthumblist li { margin: 0 1px 3px; } .imgthumblist p { margin: 0; line-height: 18px; font-size:12px} .imgthumblist div { line-height: 90px; font-size: 90px; height: 100px; display: table; } .imgthumblist div a { display: table-cell !important; display: block; 100px; vertical-align: middle; } .imgthumblist div img { vertical-align: middle; max- 100px; max-height: 100px; expression(this.width >100 && this.height < this.width ? 100: true); height: expression(this.height > 100 ? 100: true); font-size: 10px; } @media all and (min- 0px){ .imgthumblist div img { 100px; height: 100px; } } /*for Opera Only*/</style><div><ul class="imgthumblist"><li class="list2line"><div><a href="http://www.liaozhenxin.com/blog/article.asp?id=155" title="图片名称"><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/3200612221928.jpg" alt="图片名称"/></a></div><p><a href="http://www.liaozhenxin.com/blog/article.asp?id=155">图片名称</a></p><p class="smalltxt">图片数:1</p></li><li class="list2line"><div><a href="http://www.liaozhenxin.com/blog/article.asp?id=155" title="图片名称"><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/p20061222185348.jpg" alt="图片名称" /></a></div><p><a href="http://www.liaozhenxin.com/blog/article.asp?id=155">图片名称</a></p><p class="smalltxt">图片数:3</p></li><li class="list2line"><div><a href="http://www.liaozhenxin.com/blog/article.asp?id=155" title="图片名称"><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/v2006122219452.jpg" alt="特别的爱给特" /></a></div><p><a href="http://www.liaozhenxin.com/blog/article.asp?id=155">图片名称</a></p><p class="smalltxt">图片数:4</p></li></ul></div>我就不说了代码写的很清楚
<script type="text/javascript">//改变透明度参数：图片对象，透明度：1-100的值function setAlpha(imgObj,opacityValue){
imgObj.filters.alpha.opacity=parseInt(opacityValue);
} //图片的显示大小[以宽度来限制]function DrawImageW(imgObj,widthValue){ var image=new Image(); image.src=imgObj.src; 
if(image.width>0 && image.height>0){ 
if(image.width>=widthValue){ imgObj.width=widthValue; imgObj.height=(image.height*widthValue)/image.width; }else{ imgObj.width=image.width; imgObj.height=image.height; 
} } } //图片的显示大小[以高度来限制]function DrawImageH(imgObj,heightValue){ var image=new Image(); image.src=imgObj.src; if(image.width>0 && image.height>0){ if(image.height>=heightValue){ imgObj.height=heightValue; imgObj.width=(image.width*heightValue)/image.height; }else{ imgObj.width=image.width; imgObj.height=image.height; } } } //图片的显示大小[宽高同时限制]function DrawImage(imgObj,widthValue,heightValue){ var image=new Image(); image.src=imgObj.src; if(image.width>0 && image.height>0){ if(image.height>heightValue||image.width>widthValue){ var h=0,w,wflg=false; if(image.height>heightValue) wflg=true; if(wflg){ w=widthValue; h=(image.height*widthValue)/image.width; } if(h==0||h>heightValue){ h=heightValue; w=(image.width*heightValue)/image.height; } //alert(w) //alert(h) imgObj.width=w; imgObj.height=h; }else{ imgObj.width=image.width; imgObj.height=image.height; } } } function zoomImg(imgObj){ var zoom=parseInt(imgObj.style.zoom, 10)||100;zoom+=event.wheelDelta/12;if (zoom>0) imgObj.style.zoom=zoom+'%'; return false;}</script><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/3200612221928.jpg" onload="javascript:DrawImageW(this,100);" style="filter:alpha(opacity=60)" onMouseOver="setAlpha(this,100)" onMouseOut="setAlpha(this,60)" title="修改透明度"><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/3200612221928.jpg" onload="javascript:DrawImageW(this,100)" title="宽在100以内"><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/3200612221928.jpg" onload="javascript:DrawImageH(this,100)" title="高在100以内"><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/3200612221928.jpg" onload="javascript:DrawImage(this,100,100)" title="宽高在100以内"><br><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/p20061222185348.jpg" onload="javascript:DrawImageW(this,100)" title="宽在100以内"><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/p20061222185348.jpg" onload="javascript:DrawImageH(this,100)" title="高在100以内"><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/p20061222185348.jpg" onload="javascript:DrawImage(this,100,100)" title="宽高在100以内"><br><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/v2006122219452.jpg" onload="javascript:DrawImageW(this,100)" title="宽在100以内"><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/v2006122219452.jpg" onload="javascript:DrawImageW(this,100)" title="高在100以内"><img src="http://www.liaozhenxin.com/blog/attachments/month_0612/v2006122219452.jpg" onload="javascript:DrawImage(this,100,100)" onmousewheel="return zoomImg(this)" title="放大缩小">