Greetings. 

I am put this code in one page:
[[!teximg code="\frac{1}{5}" alt="1/5"]]

this is the configuration file ikiwiki.info:

add_plugins => [qw{sidebar goodstuff textile html htmlscrubber table pagetemplate teximg map meta anonok img version textile txt}]

  *Here the log*

This is pdfTeXk, Version 3.141592-1.40.3 (Web2C 7.5.6) (format=latex 2008.8.4)  5 AUG 2008 10:01
entering extended mode
 %&-line parsing enabled.
**/tmp/fb7742f8dd0c66473643ba40592e2be2.SBQfJo94ii/fb7742f8dd0c66473643ba40592e
2be2.tex

(/tmp/fb7742f8dd0c66473643ba40592e2be2.SBQfJo94ii/fb7742f8dd0c66473643ba40592e2
be2.tex

[...]

Package scrkbase Info: You've used the obsolete option `12pt'.
(scrkbase)             \KOMAoptions{fontsize=12pt} will be used instead.
(scrkbase)             You should do this change too on input line 594.

[...]

! LaTeX Error: File `mhchem.sty' not found.

Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: sty)

Enter file name: 
! Emergency stop.
<read *> 
         
l.1 ...l}\usepackage[version=3]{mhchem}\usepackage

                                                  {amsmath}\usepackage{amsfo...

(cannot \read from terminal in nonstop modes)
 

Here is how much of TeX's memory you used:
 761 strings out of 94074
 10268 string characters out of 1167096
 66007 words of memory out of 1500000
 4120 multiletter control sequences out of 10000+50000
 3938 words of font info for 15 fonts, out of 1200000 for 2000
 645 hyphenation exceptions out of 8191
 30i,1n,28p,410b,45s stack positions out of 5000i,500n,6000p,200000b,10000s
No pages of output.


Some idea ?. 

>> It looks like teximg uses some less standard LaTeX packages.  (see line 100 of Ikiwiki/Plugin/teximg.pm in the Ikiwiki source.)
>> A quick work-around for an end-user would be to install the 'mhchem' LaTeX package (look in [CTAN](http://www.ctan.org/) ).
>> A medium-term workaround would be to replace 'scrartcl' on line 100 with 'article', and delete line 101 in the teximg source.
>> Longer term it would be nice to give teximg a configurable preamble.
>> Hrm - maybe that configurable preamble should be a [[todo]]? -- [[users/Will]]

>>>Yes it works. Thanks. I am writing some code for examples.


