Optimizing filenames

Hi, i am pretty terrible at SEO, and have never even managed to find any of my sites in google, but i just had a pretty basic question. When naming a file(say for example the page is about Search Engine Optimization), what should i use in place of spaces?

ei.
search-engine-optimization.html
search_engine_optimization.html
searchengineoptimization.html

or something else, and does it make a difference if it is upper case or lower case?

ei.
Search-Engine-Optimization.html

Thanks,

Matthew

 

search-engine-optimization.html

lower case. and don't use too many hyphens..i'd say two at the most.

 

Search engines do not recognize underscores. The see it all run together. This search_engine_optimization.html is just like this: searchengineoptimization.html to the search engine. It would not recognize the space in between words.

 

either with hypen or all together. It's not good for human being too to have hyphen.