The rules defined in section 2.5.4 seem to allow numbers followed by any non-numeric characters i.e. not only is "41 " valid, but so is "41xyz". Both evaluate to 41. A value such as "41q20" would also evaluate to 41.
This is because what follows the collected sequence of numeric character is never checked.
It is unclear why a sequences of number followed by any non-numeric character should be valid.
Once the algorithm is done collecting the last numeric sequence and before returning a value, it should:
- Skip whitespace
- If position is *not* past the end of input, return an error.
The related sections are:
188.8.131.52 Non-negative integers 
184.108.40.206 Signed integers 
220.127.116.11 Real numbers 
18.104.22.168 Percentages and lengths 
Isn't it this way because that's how browsers work (interoperably)? I certainly remember <table border="5"> being the same as <table border="5px"> or <table border="5em"> or <table border="5zzz">.
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Change Description: no spec change
Rationale: The rules don't "allow" numbers; and numbers like "41xyz" aren't "valid". However, the parser does handle those errors by ignoring the invalid trailing content. That's intentional, for back compat reasons.