缓存问题

网页图片在微信加载的时候位置偏移。 最后找到原因之前调试的时候图片位置没定好，加载时访问缓存所以偏移 在html头部加上

<meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidat>

解释

<!--
    The "expires" "http-equiv" meta-tag can be used to control
    the cacheing of pages with Netscape 3.0 and later browsers.
    The 'content="0"' form tells the browser to not cache the
    page at all.
-->
<meta http-equiv="expires" content="0">
<meta http-equiv="expires" content="Tue, 14 Mar 2000 12:45:26 GMT">
<!--
    The "pragma no-cache" http-equiv meta-tag was introduced
    in the HTTP/1.1 specification.  Not all browsers or proxy
    agents may support these operations.  To be safe you may
    want to specify both expires and pragma in the file.
-->
<meta http-equiv="pragma" content="no-cache">

<!--
    The "Cache-Control" http-equiv meta-tag was introduced in
    the HTTP/1.1 specification.  The allowed "content" values
    include:
    * public - may be cached in public shared caches
    * private - may only be cached in private (client) cache
    * no-cache - may not be cached
    * no-store - may be cached but no archived
    
    Cache-Control modifiers include:
    * no-transform - proxy servers are not allowed to transform
      the cached data.
    * must-revalidate - proxy servers and other caching mechanisms
      must revalidate the original file each time the file is
      accessed.
    * proxy-revalidate - same as must-revalidate, but it only
      applies to proxy servers.
    * max-age=<seconds> - client/browser is willing to accept
      a page that is more recent than the number of seconds
      indicated.
    * s-maxage=<seconds> - same as max-age but applies to shared
      proxy servers and other shared caching mechanisms.
    
    The directive CACHE-CONTROL:NO-CACHE indicates cached
    information should not be used and instead requests should
    be forwarded to the origin server. This directive has the
    same semantics as the PRAGMA:NO-CACHE.
    
    Clients/Browsers SHOULD include both "pragma no-cache" and
    "cache-control no-cache" http-equiv meta-tags when used with
    a server not known to be HTTP/1.1 compliant.    
-->
<meta http-equiv="cache-control" content="no-cache, must-revalidate">

<!--
    Be aware that some search engines will remove pages from
    their indexes based on the "expires" meta-tag.  This
    implies that pages that identify a 'content="0"' form may
    not be indexed at all.
-->

有时间看看http协议

7.28发现加meta也没有什么卵用，缓存还是要删了微信重新安装