Do you have the following set in your user.config file?

<add key="CacheCssOnServer" value="false" />
<add key="CacheCssInBrowser" value="false" />

If not, set them and then touch the web.config (open it and then save it).

You can set these to true after you have completed your skin changes.

HTH,
Joe

After changing those cache settings you may still need to clear the browser cache one time. Visit a different site, clear the browser cache then come back to your site.

Hope it helps,

Joe

Instead of commenting out that css try changing it to this:

.skiplink {display:none;}

Note, make sure the style.css file you are editing is the one located in /Data/Sites/1/skins/skinname folder not in /Data/skins/skinname, the later is just the skin catalog, when new sites are created skins are copied from there to the /Data/Sites/[SiteID]/skins folder and those are the skins used by the site.

Hope it helps,

Joe

Yes, if you upgraded from 2.3.1 version we have re-organized the skin files to make it easier to find things since then so copy all skins form /Data/skins to /Data/Sites/1/skins since you haven't yet implemented a custom skin. Another change is that we are using text links by default now for admin links as aggregate feedback has shown the icons to be less friendly. 

If you prefer the icons you can keep the existing skins in /Data/Sites/1/skins/, but the files are organized differently so its probably stylelayout.css that has the main css.

Hope it helps,

Joe