W3C标记验证符＆符错误

Question

Is there any workaround for the w3c validation error for an & present in urls or some other place in HTML markup?
It says:

& did not start a character reference. (& probably should have been escaped as & .)

The ampersand in my case is a part of a url for gravatar thumbnail. This is the problematic part of a url:

c91588793296e2?s=50&d=http%3A%2F% .

Answer 1

Use & for literal ampersands, even in URLs.

http://htmlhelp.com/tools/validator/problems.html#amp

Answer 2

for each & sign you got write & in your example it would be:

c91588793296e2?s=50&d=http%3A%2F%

Answer 3

替换为&

Answer 4

should be:

c91588793296e2?s=50&d=http%3A%2F%.

notice the &

I know it feels wonky, but ampersands have to be encoded as html entities, which are confusingly denoted with ampersands.