Underlige warnings på http://validator.w3.org

Jeg får følgende to warnings når jeg validater min side:


Warning Line 63 column 156: character "&" is the first character of a delimiter but occurred as data.
...ument.signup.UserName.value.indexOf("&") >= 0))
This message may appear in several cases:

You tried to include the "<" character in your page: you should escape it as "&lt;"
You used an unescaped ampersand "&": this may be valid in some contexts, but it is recommended to use "&amp;", which is always safe.
Another possibility is that you forgot to close quotes in a previous tag.

Warning Line 87 column 46: character "<" is the first character of a delimiter but occurred as data.
...ument.signup.Email.value.indexOf("@")<=0 || document.signup.Email.value.index


De to linier i mit dokument er følgende:
if ((document.signup.UserName.value.indexOf("%") >= 0) || (document.signup.UserName.value.indexOf("?") >= 0) || (document.signup.UserName.value.indexOf("&") >= 0))

if (document.signup.Email.value.indexOf("@")<=0 || document.signup.Email.value.indexOf("@") == document.signup.Email.value.length-1)