How to display text as superscript in "Alt Text"?

Question

How to display text as superscript in alt text

like this:

Value¹⁰

Answer 1

Alt text is just normal text, you can try inserting unicode hypertext characters:

Value¹⁰

But if it works, it will depend on the viewer's font (and correct encoding)

Answer 2

Like knittl and SLaKs said, try using unicode character html entities.
http://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts

¹²³⁴⁵⁶⁷⁸⁹⁰

Result: 1​​23⁴⁵⁶⁷⁸⁹⁰

Bigger: 123⁴⁵⁶⁷⁸⁹⁰

For readability, though, you might just want to do something like 10^1234.
Or, for citations, anyway[1].