Synaptic and Picasa

[The Wassermans]

I'm a very new Ubuntu 8.04 user . . .. 

I tried to install Picasa from some instructions I found somewhere on
the web.  It failed and I gave up!

Today I went in to Synaptic to have a look but was presented with this
error message:

"E: Type '<!DOCTYPE' is not known on line 1 in source
list /etc/apt/sources.list.d/medibuntu.list
E: The list of sources could not be read.
Go to the repository dialogue to correct the problem.
E: _cache->open() failed, please report."

What have I done?
How do I fix it?
And then, Can some please provide some instruction on how to install
Picasa?


Dave W