问题
In html does the text inside the img tag's alt attribute require encoding/escaping?
Non encoded example:
<img src="myimg.png" alt="image description" />
Encoded example:
<img src="myimg.png" alt="image%20description" />
回答1:
No, it does not need to be encoded like a URI. However, HTML characters must be encoded, like this...
<img src="myimg.png" alt="Me & my image" />
回答2:
They do not require URL encoding, but they do require, as all XHTML attributes do, XHTML entity encoding.
Incorrect:
<img src="foo.gif" alt="Ben & Jerry's" />
Correct:
<img src="foo.gif" alt="Ben & Jerry's" />
You would also need to encode double-quotes within the values, even though you don't have to do that in general text.
Reference:
- http://www.w3.org/TR/xhtml1/#C_12
回答3:
No it does not. Encoding is for URLs as in http://en.wikipedia.org/wiki/Dream%20Theater, which the alt string is not.
You will need to use entity-encoding to escape > as >, and " as ", though. Note that that is different from URI encoding where special characters are encoded as a percent sign plus two hex digits.
回答4:
You should use HTML encoding (i.e. " becomes "), not URL encoding. If you are using ASP.NET you can achieve this with Server.HtmlEncode or better yet use the HtmlAttributeEncode method in the AntiXSS Library on CodePlex.
来源：https://stackoverflow.com/questions/1165635/does-the-img-tags-alt-attribute-require-encoding